This PDF file contains the front matter associated with SPIE Proceedings Volume 7630, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We have experimentally demonstrated simultaneous 10-Gb/s optical time-slot swapping between return-to-zero (RZ) signal format and non-return-to-zero (NRZ) signal format based on the parametric wavelength exchange (PWE) in the highly-nonlinear dispersion shifted fiber (HNL-DSF). Original RZ and NRZ signals located at two different wavelengths are exchanged after the PWE process. After exchanging between RZ and NRZ signals, the swapping ability involving two different signal formats within particular time slot has been proved. Clear open eye diagrams of periodic mixed RZ and NRZ signals are recorded on both wavelengths.

We report a new design of differential phase-shift keying (DPSK) receivers which utilize a single demodulator to receive polarization division multiplexed signals. More than 20 dB extinction-ratio can be achieved by optimizing the phase detuning with a polarization controller in the receiver. Experimental demonstrations using 20 Gb/s polarization multiplexed DPSK signals and 2¹⁵-1 pseudorandom binary sequence are conducted to show the performance of the proposed receiver. After 60 km of optical fiber transmission, the receiver has less than 3 dB power penalty at bit-error rate (BER) of 10^-9.

We demonstrate and optimize a microfluidic refractive index sensor with ultra-high sensitivity based on an acoustic grating in a solid core photonic bandgap fiber. The sensitivity of the acoustic grating's resonance is 17 900 nm/RIU which corresponds to smallest detectable changes in refractive index of 8.4×10^-6.

Simple technique is proposed for measuring distributed Raman gain efficiency spectrum in a single-mode fiber based on the bidirectional OTDR. The Raman gain efficiency spectra are successfully estimated easily from the relative-index difference and wavelength dependence of the mode field radius (MFR).

A novel simple long distance FBG sensor system is proposed and demonstrated. It can easily achieve 45dB signal-tonoise ratio (SNR) after transmitting along a 50km single mode fiber (SMF) by using only one 1W Raman pump laser source at 1395nm and a segment of 5m Erbium doped fiber (EDF) inserted before the FBG.

To cope with the development of Carrier-suppressed-return-to-zero-on-off-keying (CSRZ-OOK) modulation format, it is of great significance to investigate all-optical logic gates to process CSRZ-OOK format signals. To the best of our knowledge, for CSRZ-OOK signals, only logic AND gate has been demonstrated while other logic functions haven't been explored until now. In this paper, an all-optical logic unit to process CSRZ-OOK signals based on four-wave mixing (FWM) arising in a semiconductor optical amplifier (SOA) is proposed. A logic OR gate and two logic AND gates with the CSRZ-OOK format unchanged could be simultaneously achieved without reconfiguration in this single unit. The performance of 40 Gb/s logic operation is firstly evaluated with numerical simulations by a comprehensive dynamic model considering three-input induced FWM in an SOA. Then, experimental demonstrations at 10 Gb/s with clear waveforms and high extinction ratios (ERs) further verify the logic integrity of this scheme.

A novel kind of all-optical dynamic grating with the reflectance and the center wavelength controlled by another optical wave can be realized based on Brillouin scattering in polarization-maintaining optical fibers. This grating, called Brillouin dynamic grating (BDG), has proved to be useful based on its unique characteristics in several applications such as high performance distributed sensors and optically-tunable delay lines.

Temperature sensitivities of D-shaped fibers with specified surface structures such as thin film and periodic grating are investigated. The photo resister overlay can induce the evanescent field coupling of the core mode to the cladding mode in the overlay. The mode coupling can be modified by the overlay structures such as a single layer and periodic grating. The temperature sensitivity of D-shaped fibers with versatile overlay structures is also changed.

The fluorescence intensity ratio (FIR) technique for optical fiber-based temperature sensing is discussed in many previous papers. But in the high temperature sensing the FIR technique has been researched a little. In this paper, the temperature dependence of fluorescence in erbium-doped fiber between ~700 and ~1300 °C; is discussed and experimentally demonstrated. 1450nm and 1530nm wavelengths are chosen to calculate the FIR, and the temperature coefficient could achieve ~ 0.003dB/°C.

A novel scheme for tunable optical pulse generation based on fiber sagnac loop was proposed and studied. The key parameters of the optical pulse were analyzed and testified by simulations and experiments. The repetition rate of optical pulse is twice the frequency of external square wave modulation signal and can be tuned directly by varying modulation frequency. The maximal peak value can be achieved when the peak-peak value of the square wave modulation signal was equal to the half-wave voltage of the phase modulator. Experimental results agree well with theoretical predictions and simulations.

We demonstrate a simple method to generate a high speed pulse train from a low speed pulse source by spectral filtering using a high finesse fiber Fabry-Pérot interferometer. Reasonably stable 100 GHz pulses at 1550 nm were obtained from a 10 GHz mode-locked fiber laser.

We have theoretically studied pulse propagation in a normal-dispersion optical cubicon fiber amplifier (NDOCFA) with an arbitrary longitudinal gain proflie, and have obtained an analytic solution for the nonlinear Schrödinger equation that describles such an amplifier. The results show that the characteristics of self-similarity and linear chirp will be lost due to third-order dispersion. However, by using a dispersion compensation technique, one can obtain efficient and high-quality compressed pulses. The numerical simulation is consistent with the analytic results.

A wavelength tunable polarization OTDR utilizing a semiconductor optical amplifier for the received signal amplification is proposed in order to realize stable operation. Measurement experiments are carried out for a fiber link with a length of 5.7km and the state of polarization change along the fiber link is successfully estimated.

We propose a novel structure of single-polarization single-mode(SPSM) holey fiber designed based on resonant coupling effect. The proposed fiber is able to achieve SPSM operation over an ultra-broad bandwidth as large as 920nm ranging from 1.48μm to 2.4μm, within which only one polarization state of the fundamental mode can be effectively guided. With the aid of six smaller holes around the central core, the effective mode area of the fiber is enlarged and the chromatic dispersion curve is flattened. The numerical results indicate that the proposed fiber achieves nearly zero ultra-flattened dispersion over a wide spectral range and the effective mode area is approaching ~78μm2 at 1550nm. Moreover, the structure shows superiority in output beam quality owing to the symmetry of the central core region, and also exhibits great modal compatibility with SMF.

A Polarization measurement using DSP-based control system has been demonstrated in the experiment. The normalized Stokes parameters and the degree of polarization which are varying at the speed of in the order of millisecond are measured in real-time manner.

All-optical logic gate is a basic and crucial element for optical signal processing. In this paper, we propose a 4×2 encoder based on two dimensional triangular lattice photonic crystals composed of cylindrical silicon rods. The main structure of the device is a combination of both line defect Y branch and coupler photonic crystal waveguides. The computational simulation is carried out by using a finite-difference time-domain (FDTD) method. The simulation results show that the proposed all-optical photonic crystal waveguide structure could really function as a 4×2 encoder logic gate. In addition, the distance between coupler photonic crystal waveguides, the length of coupler waveguides and the distance between line defect Y branch waveguide structure are optimized for achieving the optimal performance for the proposed encoder logic gates. This device is potentially applicable for photonic integrated circuits.

A Folded Mach-Zehnder interferometer (FMZI) in a two-dimensional photonic crystal is proposed. The FMZI consists of one splitter and several mirrors. Light propagates between them employing self-collimation effect. Its two interfering branches have different path lengths. The two complementary transmission spectra at two FMZI output ports are both in the shape of sinusoidal curves and have a uniform peak spacing in the frequency range from 0.255c/a to 0.270c/a. The peak spacing becomes smaller when the length difference between the two branches is increased. As self-collimation light beams can cross each other without coupling, this FMZI is much smaller than non-folded interference-type filters in photonic crystals. This FMZI may work as a wavelength division demultiplexer in high-density photonic integrated circuits.

We propose and experimentally demonstrate a novel compact and integrated terahertz waveguide, which consists of silicon photonic crystals with triangular lattice and a line defect waveguide in photonic crystal (PC) slabs. We also directly measured the propagation loss of the line defect waveguides and obtained a value of 0.99dB/mm. The observed waveguiding characteristics agree very well with three-dimensional finite difference time-domain calculations.

Based on the theory of one-dimensional photonic crystal, an asymmetrical interleaver filter is proposed. It is composed of cascaded thin-film glass cavities. Each thin-film glass cavity is formed by evaporating several layers of reflecting films on two surfaces of glass medium. Compared with other proposed structures, the proposed interleaver structure is not only very simple but also easy to accomplish. Moreover, flat passband and stopband can be obtained by the interleaver. A design example of a 50 GHz interleaver filter with duty cycle of 1:5 is presented. The influence of each structural parameter on spectral performance, especially for the duty cycles is discussed. On this basis, design results of interleaver filters with duty cycle of 1:3 and 1:4 are shown and analyzed. A design example of an interleaver filter with five cascaded cavities is given at last.

We successfully generated 114-Gb/s PDM-8QAM optical signal by novel scheme. Intradyne coherent detection of PDM-8QAM optical signal with robust blind polarization de-multiplexing has been demonstrated by using a new cascaded multi-modulus equalization algorithm. With RZ-shaped PDM-8QAM modulation and the proposed blind polarization de-multiplexing algorithm, we demonstrate a record 33.9-Tb/s fiber capacity (320×114Gb/s) being transmitted over 580km of ultra-low-loss SMF-28 fiber utilizing C+L-band EDFA-only optical amplification and single-ended coherent detection technique, at a spectral efficiency of 4.2bit/s/Hz. Utilizing only C-band EDFA, we also demonstrate that 16.9-Tb/s capacity (160×114Gb/s)) can be transmitted over 640km of standard SMF-28 fiber.

The influence of pump power on the output characteristics of multiwavelength erbium-doped fiber laser, which employs the effect of the intensity-dependent loss induced by a power-symmetric nonlinear optical loop mirror, is investigated. The results of studies show that the multiwavelength output characteristics including the number, the flatness and the spectral region of output wavelength can be controlled by adjusting the pump power. To optimis the multiwavelength operation, a suitable pump power must be chosen for this kind of laser.

Passive harmonically mode-locked erbium-doped fiber ring laser with scalable repetition rates up to 1.2 gigahertz is experimentally demonstrated, to our best knowledge, which is hitherto maximum repetition rate from only-erbium-doped fiber laser. Owing to the acousto-optic effect, stable passive harmonically mode-locking can only occur at some certain discrete repetition rates corresponding to resonant frequencies of transversal acoustic wave induced by propagating optical pulses in fibers.

A passive Q-switched Yb-doped microstructure fiber (MF) laser is demonstrated using a GaAs wafer as the saturable absorber. A high Ytterbium-doped fiber with a core diameter of 21 μm and a numerical aperture of 0.04 was used as the active fiber. The large-diameter core allows for greater energy storage than conventional single-mode core designs and the small NA of the core ensures the good beam quality of the laser. A pulse duration as short as 80 ns was obtained with the maximum repetition rate of 830 Hz. The maximum average output power is 5.8 W at 1080 nm wavelength.

The optical fiber delivery laser power technology in laser flexible manufacturing system is introduced. The characteristics of optical fiber delivery Nd:YAG pulsed laser power through multimode silica fiber are experimentally researched, which include beam spatial characteristics of fiber exit beam and the capacity of optical fiber delivery high power laser. The effects of laser injection condition and optical fiber bending radius on optical fiber delivery laser beam system are analyzed. The morphology characterization of laser induced damage to optical fiber end-faces were measured and investigated. The model of laser induced damage to fiber end faces is presented.

In this paper, we describe and investigate a new UV photo-writing setup using Travelling Interference Fringe (TIF) technique for Fiber Bragg Grating (FBG) realization. A continuously moving fringe pattern is generated using two electro-optical UV modulators and is synchronized with the fiber moving speed. FBG parameters such as chirp, phase shift and apodization profile can be controlled with high precision. This method is used to realize repeatable, flexible and complex profile spectral phase OCDMA encoders/decoders. Experimental realization results in good agreement with numerical simulations are presented and discussed. The obtained encoders/decoders are tested within a system setup using a supercontinuum optical source.

By using a fiber optical parametric amplifier, we demonstrate a novel pre-amplification scheme to improve receiver sensitivity for 10-Gb/s non-return-to-zero on-off keying (NRZ-OOK) format with dual-end superposition of signal and idler in the optical parametric amplifier (OPA). We achieve receiver sensitivity of -40.5 dBm at BER = 10^-9. Compared to its single-end counterpart, the receiver sensitivity can be improved by 2 dB.

The polarization sensitivities of demodulation techniques for tilted fiber Bragg Grating (TFBG) refractometer are investigated theoretically with the complex mode based coupled mode theory. The use of perfectly matched layer (PML) technique simplifies the radiation mode model. The numerical results show that both the normalized area detecting technique and the power-referenced demodulation technique are highly polarization sensitive, the polarization sensitivity increases with the grating tilted angle, thus, precise polarization control is essential in both of the demodulation techniques.

The unified coupled-mode formalism derived from Maxwell's equation is employed to analyze the add/drop filters using a Bragg grating assisted mismatched coupler. An add/drop filter using a Bragg grating-assisted mismatched coupler is fabricated and tested. The maximum reflectivity, 3dB bandwidth, insert loss at the drop port and reflective loss at the input port of the filter are measured to be about 12 dB, 0.2 nm, 3.91 dB and - 7.39 dB, respectively.

A triplexer based on silicon nanophotonic wire structure consisting of two Bragg grating-assisted directional couplers is proposed, which can multi/demultiplex three different wavelengths through a compact device. The device has low loss, low crosstalk, and a footprint of only 210 ×40 μm. The 1-dB bandwidth for the three channels located at 1310, 1490 and 1550 nm are 110, 20, and 20 nm, respectively.

We propose a technique to improve the performance of high index contrast Multimode Interference (MMI) couplers. It is shown that imaging errors can be almost completely removed if the refractive index profile of the multimode region is properly designed. The proposed technique has been applied to design a 2x4 MMI 90º hybrid on SOI submicrometer strip waveguides (silicon-wires). Results show that the optimized device exhibits an almost ideal performance.

We numerically investigate a new function modified from Hamming function to apply in weighting the waveguide structure of a mismatched optical coupler with the characteristics of low crosstalk, short length, and broad C+L-band. The full factorial design and beam propagation method are being used to seek the optimal structure parameters of coupling waveguide. This modified Hamming weighting function (M-HWF) is proved to have the superior performances to Hamming weighting function (HWF) in several ways. In theoretical computation, the M-HWF and HWF waveguides have the coupling lengths of 11 mm and 16 mm, respectively at crosstalk of -40 dB and operating wavelength of 1.57 μm. After the numerical design of waveguide structure parameters, the M-HWF also obtain a shorter coupling length of 4.50 mm than coupling length of 5.90 mm of HWF at crosstalk of -40 dB and within the C+L-band (1.53~1.61 μm). The M-HWF waveguide with the shortest coupling length of 4.5 mm can even reach a broader bandwidth between 1.50 and 1.70 μm.

A newly self-developed Broadband weighting function is presented to show the excellent results comparing with the Blackman and Hamming weighting function in applying to the waveguide structure of mismatched optical couplers for the demand of short-length, C+L-band, and low crosstalk. It is found that the coupler with the Broadband weighting function can reach the bandwidths between 1.360 to 1.700 μm with a coupling length of 2.5 mm and crosstalk of -35 dB. Obviously, the Broadband WF is suited in weighting the waveguide structure of a mismatched optical coupler to obtain a short coupling length, low crosstalk, and broad bandwidth.

We report the fabrication and accurate measurement of propagation and bending losses in silicon wires with submicron dimensions fabricated on silicon-on-insulator wafer. Propagation loss of 0.71±0.03dB/mm for the TE polarization was measured at the 1.55μm. Loss of per 90º bend is measured to be 0.01dB for a bending radius of 5μm. Three types of compact MMI splitters with different splitting-ratios were fabricated and measured. The splitting-ratios are respectively 50:50, 15:85 and 28:72. They exhibited low excess losses of about 1.5~3.9dB. The splitting-ratios were consistent with the design values.

The unified coupled-mode formalism derived from Maxwell's equation is employed to analyze the add/drop filters using a Bragg grating assisted mismatched coupler. By writing a linearly chirped Bragg grating over the uniform coupling region of the coupler, a filter with maximum reflectivity and 3dB bandwidth at the drop port about 20 dB and 0.8 nm, respectively, is obtained. The experimentally measured results are in good agreement with the numerical calculations. A broadband add/drop filter using a Bragg grating-assisted mismatched coupler can be obtained by writing a linearly chirped Bragg grating over the uniform coupling region of the coupler.

We report a novel design of photonic crystal fiber (PCF) with a rectangular array of four closely-spaced, highly elliptical air holes in the core region and a circular-air-hole cladding. The proposed PCF is able to support ultra-wideband singlepolarization single-mode (SPSM) transmission from the visible band to the near infrared band. With the aid of the inner cladding formed by the central air holes, one polarization of the fundamental mode can be cut off at very short wavelengths and ultra-wideband SPSM propagation can be achieved. The inner cladding also suppresses the higher order modes and allows large air filling fraction in the outer cladding while the proposed fiber remains SPSM, which significantly reduces the mode effective area and the confinement loss. Our simulation results indicate that the proposed PCF has a 1540 nm SMSP range with < 0.25 dB/km confinement loss and an effective area of 2.2 m2. Moreover, the group velocity dispersion (GVD) of the proposed PCF can also be tuned to be flat and near zero at the near infrared band (~800 nm) by optimizing the outer cladding structure, potentially enabling many nonlinear applications.

We propose an ultra compact structure for Dense Wavelength Division Multiplexing (DWDM) systems using resonance cavity in Photonic Crystal (PC) structure. To the best of our knowledge, this is for the first time that a PC-based demultiplexer has been achieved with 0.8nm channel spacing, -18.77dB and 4170 average crosstalk and quality factor, respectively without using particular materials or complexities in fabrication. Two-dimensional (2D) Finite-Difference- Time-Domain (FDTD) method is chosen for simulation in this work.

We experimentally demonstrate all-optical signal processing functions using silicon microring resonators with a 450×250-nm cross section. These results include slow-light delay of phase-modulated data and microwave photonic signal, wavelength conversion/multicasting, format conversions, optical differentiation, and concentric micro-ring resonators with deeper notches for label-free bio-sensing applications.

Small suspended SU-8 optical waveguides with a high refractive index contrast are designed and optimized. The singlemode condition and the bending characteristics of the present waveguide are numerically calculated by using a fullvectorial finite-difference method. Pure bending losses and transition losses of bending waveguides with different bending radii and different core widths are studied. The simulation results show that a wider core is helpful to reduce the pure bending loss. For example, when the core width is chosen as 2 m, a very small bending radius (~5 m) can be achieved. However the transition loss is high. When a small total bending loss (<0.1dB/90º bend) is required, the minimal bending radius is about 7 m when an optimal offset is introduced. A crossing structure with two arms to support the suspended waveguides is designed and optimized by using a two-dimensional finite-difference time-domain method. The structure parameters (e.g., the expanding width, the taper length and the length of the insert straight section) of the crossing structure are optimized to minimize the excess loss. The optimal crossing structures exhibits a low excess loss (<0.1 dB) and performs well in a wide wavelength range (1500 nm~1600 nm).

A silicon cross-slot waveguide filled with electro-optic polymer is proposed to release the polarization-dependent issue of the electro-optic modulator. There are two slots in both the horizontal direction and vertical direction, so this waveguide structure can confine both the TE and TM modes. The four silicon regions can be lightly doped as the electrodes. There is slanted electric field in the slot region when the voltages are applied on the electrodes. The electric field component act at principal optical axis whose electric-optic (EO) coefficient is r₃₃ or r₁₃ can be adjusted by changing the voltages on the four electrodes. With optimal voltages, the effective refractive index of the TE and TM modes can be changed equally. The Mach-Zehnder modulator based on cross-slot waveguide can achieve polarizationinsensitive.

This paper theoretically investigates spectral characteristics of the 3×2 microring resonator array, with its analytical model developed firstly. Simulation results show that the case of the ring-bus coupling coefficient smaller than the ringring coupling coefficient is suitable for box-like filters. After design principles are given, the optimization process are carried out by evaluating the side lobe rejection ratio, the passband ripple rejection ratio and the roll-off coefficient of the passband edge. The FWHM of the designed box-like filter can be adjustable in a flexible range.

An integrated optical chip based on an array of silica waveguide Fabry-Perot filters with dielectric mirrors has been fabricated as part of a photonic microwave channelising receiver. The channeliser is based on a vernier architecture. Thin-film heaters on the surface of the waveguide filters enabled the resonant frequency of the filters to be tuned. Filter 3dBe bandwidths of ~1 GHz were measured.

We demonstrate the fabrication of a kind of asymmetrical twin core fiber, which is easy spliced with standard single mode fiber. This fiber is designed to be used for passive mode-locking in fiber lasers.

A new structure of single polarization single mode (SPSM) microstructured polymer optical fiber (mPOF) is proposed and numerically analyzed by using a full vector finite element method with anisotropic perfectly matched layers. The cutoff wavelength of two linearly polarized states can be design by varying the structure parameters of mPOF. The confinement loss are also numerically calculated and optimized at communication wavelength of polymer optical fiber (POF) of 650 nm. From the numerical results it is confirmed that the proposed fiber is low-loss SPSM mPOF within the wavelengths ranging from 0.63 μm to 0.73 μm, where only the slow-axis mode exists and the confinement loss is less than 0.05 dB/m.

Absorption coefficience of Tm³⁺ ions in Tm ³⁺ /Yb³⁺ codoped tellurite glass have been analyzed by using the J-O theory. The J-O parameters are calculated to be Ω₂ = 11.11×10^-20 cm², Ω₄ = 3.5×10-20 cm2 and Ω₆ = 3.6×10^-20 cm². Spontaneous radiative transition probabilities, branching ratios and radiative life time of Tm3+ ions are also calculated, the calculation results indicate that it is difficult to get S-band amplification through single 808 nm laser pump in this glass, this is tested by 808 nm single wavelength pump experiment. The Yb³⁺ codoping with Tm³⁺ and energy transfer process between them make 980 nm single wavelength pump scheme possible to get S-band amplification, experiment results indicate that 980 nm pump energy absorbed by Yb³⁺ is transferred to Tm³⁺, consequently, the low cost 980 nm pump scheme could make it become promising material for S-band amplification.

Copper ion exchange technique was used to fabricate soda-lime glass planar waveguides. Prism coupling method was applied to measure the effective indices, and the refractive index profiles were reconstructed through Inverse WKB (IWKB) method. Optical absorption and photoluminescence analysis were carried out as well. The emission spectra centered at 520nm are attributed to Cu⁺ located in distorted octahedral sites. It was found that the ion exchange time and temperature both play an important role in the waveguides luminescence properties. The emission spectra intensities decrease with the ion exchange time increasing. The emission peak wavelength slightly blue shifts as the ion-exchange time increasing as well. The emission band intensity nearly increases consistently with the ion-exchange temperature increasing within proper ion-exchange time. Different excitation wavelengths were tested as well in order to study the site effect on photoluminescence properties.

To meet the application demand of optical communication system, a new type of variable optical power splitter (VOPS) based on slot waveguide by adjusting manually is proposed in this paper. The device is designed by using the principle of optical field effect. It has an import port which provides import power, and two output ports, the power of which is divided dynamically by changing the width of the gap between two slot waveguides. This paper can specify the operation principle of the device, test its important technical indicators and analyze experimental datum. Experimental results show that the device can realize light distribution of the single wavelength and multiple wavelengths and that the power splitting ratio is dynamically tunable and the tuning range can be 1-25dB, which ensures rapid organization and deployment of communication network.

The athermal all-polymer waveguide microring resonator is realized by selecting polymer substrate with proper thermal expansion coefficient to substitute the silicon one. The designed results show that the maximal resonant wavelength shift is -0.0085nm and the maximal temperature dependent wavelength shift slope is -0.0009nm/K when the temperature varies from 20°C to 65°C.

We propose a novel design for photonic crystal fiber, which has flattened-dispersion, high nonlinear coefficient and low confinement loss for supercontinuum generation. The proposed fiber needs appropriate number of design parameters. Results show that eight-ringed photonic crystal fiber is obtained with nonlinear coefficient greater than 33W^-1 km^-1, and small dispersion slope 2.00×10^-3ps/nm²/km in the telecommunication window. Ultra flattened dispersion of -1.65~ 0.00 ps/nm/km and confinement loss in super low order of 10^-4dB/km are simultaneously obtained ranging from 1.45μm to 1.65μm. It's shown that through numerical analysis the novel micro-structured optical fiber with small normal group-velocity dispersion and nearly zero dispersion slope offers the possibility of efficient supercontinuum generation in the telecommunication window using a few ps pulse. supercontinuum with 70nm-bandwidth at 1550nm is achieved through only 150m-long fiber.

Design optimization of a pure silica dual-core photonic crystal fiber for broadband dispersion compensation is proposed to match the relative dispersion slope of the standard single-mode fiber. The influence of the three diameters of the air-holes in the outer cladding upon the dispersive and slope-matched property is investigated and a dispersion value of -3179.9 ps • ;nm&-^-1 • km-^-1 at 1550 nm has been predicted. The dispersion of the standard single-mode fiber, which is 187 times the length of the dual-core photonic crystal fiber, can be compensated (to within 0.12%) over the entire C band / (to within 0.56%) over the 100-nm broadband centered at 1550nm .

A compact in-line interferometer is demonstrated by splicing a piece of two-mode photonic crystal fiber (TPCF) between two segments of single mode fiber (SMF). The TPCF is completely homemade and carefully simulated by finite element method based on the real cross section. It is firstly verified that the interference occurred between LP01 and LP11even modes and the period of the interference pattern was inversely proportional to the length of TPCF. The temperatures and strain induced interference pattern shifts with sensitivities of -43pm/°C and -0.62pm/με are experimentally monitored. ©2009 Optical Society of America.

We present a numerical investigation of nonlinear propagation of chirp-free femtosecond pulses at 1550-nm wavelength in a nonlinear photonic crystal fiber (PCF) with anomalous dispersion. The PCF has a second-order dispersion of - 8.67 ×10⁴ fs²/m, third-order dispersion of 2.8 x 10⁵ fs³/m and nonlinear coefficient of 11 W^-1km^-1 at 1550 nm. The simulation results show that efficient spectral compression of unchirped ultrashort pulses is induced in PCF when the input pulse parameters satisfy the condition 0.6< N<0.7for the soliton number N. It is found that the compressed spectral width is strongly dependent on the initial peak power and propagation length of the incident pulse. A compression factor up to 7 can be achieved. With the PCF, efficient spectral compression can take place in the wavelength range of 1530 ~ 1570 nm covering the C-band. This spectral-compression scheme offers much promise for laser spectroscopy, optical information technologies and high-power fiber-laser systems.

Fiber optical parametric amplifiers (OPAs) are based on the third-order nonlinear susceptibility of glass fibers. If two strong pumps and a weak signal are fed into a fiber, an idler is generated. Signal and idler can grow together if pump power is high enough, and phase matching occurs. Until recently, impressive performance of fiber OPAs has been demonstrated in different respects. However, secondorder effects should be addressed before OPAs can be utilized in practical applications. Here we report some of these effects, either exploiting them as in the parametric processor such as optical logic gates, inverted and non-inverted wavelength converter, and ultra-wideband monocycle and doublet pulses generator, or suppressing them as in the optical amplifier for WDM systems.

We propose and demonstrate a novel approach to implement a multi-tap photonic microwave filter. By using a twopump fiber optical parametric amplifier (OPA), the number of signal laser sources needed is only half of the number of filter taps because new frequency components idlers are generated. Moreover, the free spectral range (FSR) of the proposed filter can be changed by simply changing the wavelength spacing between the signals. In our experiment, an 8- tap photonic microwave filter has been demonstrated using 4 signal laser sources, with FSR tuning range from 1.18 GHz to 2 GHz which shows consistency between experimental and theoretical results.

The experimental study on an all-fiber laser pulse amplifier system using homemade double-cladding Yb-doped fibers as gain media is presented. Secondary pulse phenomenon produced in the pulse amplifier system is analyzed and investigated. We find that the phenomenon depends a lot on the quality of splicing between different fibers and the amplification multiple. By controlling the pump power and amplification multiples of the amplifier and trying different splicing parameters, we can get stable high power pulse lasing output. Finally, using the Yb-doped double-cladding fiber(YDCF) and master oscillation power amplification (MOPA) techniques, a stable all-fiber pulse amplification system is obtained, with lasing wavelength at 1064 nm, 20 ns line-width pulses, average power of 2.4W and repetition rate of 50kHz.

A new adaptive erbium-doped fiber amplifier (EDFA) is proposed. In the amplifier, an array of 1×2 optical switches is controlled to select the optimum length of erbium-doped fiber for different input power, and meanwhile pump power is regulated, so good adaptivity for different applications can be obtained. Simulation experiments have demonstrated that this amplifier can get high performance. It can be applied as preamplifier and line amplifier as well as power amplifier.

We propose and experimentally demonstrate a novel FBG dual-wavelength fiber laser sensor based on the beat frequency demodulation technology. The dual-wavelength beat frequency sensing signal of about 5.224 GHz has been obtained in a photodetector and observed by a radio-frequency spectrum analyzer (RFSA). Furthermore, by employing a LiNbO3 modulator, the high-frequency beating signal can be tuned arbitrarily to tens or hundreds of MHz without distortions. Thus a very cheap and low-frequency RF spectrum analyzer can be used in frequency signal detection. When a strain is applied on the sensor, the beating signal will shift with a stain sensitivity of about (-3.92) kHz/με.

A 1X2 POF splitter based on a Y-branch metal hollow POF coupler design has been developed. The device is composed of three sections: an input POF waveguide, an intermediate hollow waveguide taper and output POF waveguides. Simulation based on non-sequential ray tracings have been performed on the POF splitter. Low cost aluminum based material has been used for the device substrate. Fabrication of the POF splitters are done by producing the device mold insert using high speed CNC machining tool and short POF fibers at the input and output sections are inserted inside the mold insert before the interfaces of the hollow waveguide taper. The POF splitter has an average insertion loss of 5.8 ± 0.2 dB, excess loss of 2.8 dB and coupling ratio of 1:1. A video-over POF system test-bed consisting of a POF video transmitter and receiver has been constructed with a total transmission length of 10 m. The POF splitter has been tested in the video-over POF system and shows no significant signal degradation.

We present a new design of wavelength division demultiplexer based on self-imaging principle in the multimode interference (MMI) structure. We simulated an 8-channel wavelength demultiplexer with high quality factor in the telecommunication range. The structure has been designed with multi-stage multimode interference couplers. The principle of the design of structure can be extended to N-channel wavelength division demultiplexer. To the best of our knowledge, this work presented for the first time in MMI structure with almost 5nm channel spacing and 2451 average quality factor. Output wavelengths that are achieved from the first to the latest outputs are 1545nm, 1564.4nm, 1535nm, 1554.37nm, 1530nm, 1549.9nm, 1540nm, 1559.5nm, respectively. The beam propagation method is used for simulation of this device.

Based on Fabry-Perot structure, a multiple-channel filter is obtained in theory by changing the structure of spacer layers. This paper is concerned with the design of optical filters, based on thin-film interference, for multichannel optical communication systems with Ta₂O₅ and SiO₂ materials for 1550 nm operation. The performance of the filter configuration is analyzed and the numerical results of the optimization parameters, such as central wavelength, 3-dB bandwidth, figure of merit and ripple in the passband, are reported. The variation of these parameters is also studied for various modified filter configurations. The angular performance of the filter is investigated in terms of spectral shift of transmittance towards shorter wavelengths. It is concluded that the width of adjacent routeways can be changed by changing the structure of spacer layers. The variation of these parameters is also studied for adding irregularly suited layers. The layer sensitivity of the ultra broadband multichannel thin-film-based optical filter, is thoroughly analysed.

A compact in-fiber Mach-Zehnder interferometer comb-filter is demonstrated by splicing a section of twin-core fiber (TCF) between two single mode fibers (SMFs). The temperature and strain induced wavelength shifts of the interference fringes are experimentally monitored. Redshift (i.e., wavelength shifts to the longer wavelength side) is observed with sensitivity of about 0.037 nm/°C for increased temperature, whereas blueshift (i.e., wavelength shifts to the shorter wavelength side) is observed with sensitivity of about 0.866 pm/με for applied strain changes. This device is relatively simple to fabricate and expected to have applications in high temperature or strain fiber optic sensors and the multiwavelength fiber lasers.

The properties of glass-clad fibers containing cores of phase pure and highly crystalline silicon and germanium are reviewed. Although further optimization is required, losses of about 4 dB/m have been achieved at 3 μm and suggest that such semiconductor core fibers could be of practical value for nonlinear and infrared applications.

Recently, as the continual development of services and needs, people have a higher expectation on the optical communication system especially the passive optical network (PON). Deciding which kind of fiber to be the optimal media for PON is becoming a critical problem. This paper analyzed the feasibility for the applying of multimode fiber (MMF) in the future long haul, high bit-rate, and large capacity PON, and summarized the strengths and weakness of MMF. Then, initiating from the waveguide theory in the weakly guiding fiber and neglecting the intra-modal dispersion as well as nonlinearity, we built a simple model for multimode fiber, based on which we made analysis, research and comparison through simulation experiments on some performance improving techniques of MMF: offset launching, mode size changing, ring launching and feedback equalization. The simulation results demonstrated that the combination of field shaping and feedback equalization can obviously improve the transmission properties of MMF, because of which, the 10Gbit/s data can travel in the MMF for more than 1km.

We show wave breaking (WB) can occur in a dispersion decreasing fiber with normal group-velocity dispersion preceding the parabolic pulse formation (PPF), and the distance where it happens can be described by two equations. Based on the transformation of a nonlinear Schr dinger equation with the typical decreasing dispersion into the form of the uniform dispersion and "equivalent" gain, the first equation is obtained to determine the virtual WB distance. The corresponding real distance can then be acquired from the second equation derived from the fiber dispersion distribution function. Both the analytical results are confirmed by the numerical simulations of the two forms NLSE, and illustrated by the chirp oscillations appeared in the pulse edges, respectively. We further demonstrate that the spectral broadening of the pulse is quite different from that of the pulse temporal evolution during the PPF process. In the initial stage, the spectral broadening is dominated by the expansion of ripples in the central part of pulse caused by self-phase modulation (SPM); while in the last stage, it is dominated by the widening of sidelobe in the pulse wings caused by four-wave mixing (FWM). These facts reveal that FWM also plays an important role in the process of PPF besides SPM while the WB point is the very threshold that FWM begins to take effect.

A simple technique for measuring fiber parameter distribution of the pure silica core fiber using a conventional OTDR is proposed. This technique is based on the relationships among fiber parameters and the bidirectional OTDR technique. The fiber parameter distributions are successfully evaluated for a silica core fiber link.

In this work, we demonstrate two- and three-dimensional (3D) simulations of an active silicon-based photonic crystal chromatic dispersion compensator utilizing the free carrier dispersion effect. The device has a low power consumption of 114nW and its intrinsic device modulation speed is predicted to function at 40.5MHz. Due to the device architecture, simulation must be carried out in 3D so as to fully encapsulate the effects of the photonic crystal contributions in the active silicon. The novel device allows waveguiding and electrical transport to be individually tailored to a large extent.

Broadband integrated Er-Yb codoped phosphate glass waveguide amplifier based on cascaded long-period waveguide grating gain-equalizer is proposed. The proposed cascaded long-period waveguide grating gain-equalizer consists of some different long-period waveguide grating filtering unit cells, and each cell can suppress certain peak gain at a specific wavelength. The intrinsical gain spectrum of amplifier is obtained by solving a set of rate and power propagation equations with overlapping integral-Runge Kutter method. The effect of the transmission spectrum of the proposed cascaded long-period waveguide grating on the flattening gain of Er-Yb codoped phosphate glass waveguide amplifier is discussed. The transmission function of the cascaded long-period waveguide grating filter is obtained.

This paper presents a bend-bend coupler for an ultra-small microring resonator based on Si nanowires in order to reduce the mode-conversion loss at the coupling region. And relatively large amplitude coupling coefficient and low coupling loss are achievable due to the long coupling length of the bend-bend coupler.

A novel method to compensate dispersion and dispersion slope at the same time by using fiber Bragg grating written on the tapered core fiber has been presented. The fabrication method about this kind of tapered core fiber has been realized by precisely controlling the fiber's diameter during the process which is drawing the preform into optical fiber. The fiber grating written on this kind of fiber has parameter as 3dB bandwidth 0.861nm. Its dispersion value is - 1159ps/nm (within 0.8nm bandwidth), and the dispersion slope is -1.3 ps/nm². These characteristics of the grating make it can be used in high speed optical fiber communication systems which need the dispersion and dispersion slope be compensated at the same time.

The simulation model to bistable characteristics of grating is established by numerically solving the nonlinear coupledmode equations of Fiber Bragg Grating using 3-stage 4-order semi-implicit Runge - Kutta method. The impact of the grating parameters and operating point on S-shaped hysteresis loop parameters is researched. The results show that the area of S-shaped hysteresis loop, bistable operating condition, bistable threshold and dynamic range can be adjusted by changing the operating wavelength and grating parameters, such as grating length, grating apodization and average refractive index modulation depth of grating.

We propose a multiwavelength erbium-doped fiber (EDF) ring laser using a Fabry-Perot etalon inside the ring cavity with optimal fiber length to satisfy the least common multiple number for generating multiwavelength at room temperature.

Here we demonstrate a supercontiuum spectrum generated in a tapered fiber pumped by a Ti sapphire laser with 130fs pulse width at 800nm centre wavelength. The tapered fiber with the diameter of 1.25μm and the length of 16cm was made by using a tapered machine. The supercontiuum range is from 500nm to 900nm. We simulated the supercontinuum with the nonlinear Schrodinger Equation and discussed the affecting factors. In some conditions, the experimental results are agreed very well with the theoretical analyses.

A novel and simple design method based on pole-zero diagram is proposed for optical interleaver based on Michelson Gires-Tournois interferometer (MGTI) with arbitrary cascaded reflectors. Digital filter model which is equivalent to the MGTI optical interleaver is derived firstly. Then on the basis of it, the transfer functions of two output ports of the interleaver are simplified and all the design parameters of the interleaver can be obtained conveniently by the use of the mature design principle of elliptic filter and pole values. The two output spectrums obtained has the wide flat passband (and stopband) width and high isolation simultaneously. Compared with other existing design methods, the proposed method is simpler and more efficient, especially for interleavers with GTE composed of much more reflectors. Design examples of the interleaver with different cascaded G-T etalon structure are given.

We demonstrate a novel fiber-optic hydrophone with a mechanical anti-aliasing filter of side cavities. The amplitude and phase frequency response properties are presented with an acoustic equivalent circuit. Theoretical results show that the hydrophone has very flat low frequency response, and can greatly attenuate high frequency sound. The response curve has three resonant frequencies and an inverse resonant frequency, which is induced by the side cavities and contributes much to the high frequency attenuation. The hydrophone is tested in a standing-wave tube filled with water, and the measured frequency responses accord well with the theoretical results.

A widely tunable single-wavelength Brillouin fiber laser (BFL) incorporating a bismuth-based erbium-doped fiber (Bi-EDF) is proposed. The 52 cm-long highly erbium-doped Bi-EDF provides broadband gain extending from the C-band (1525-1565 nm) to the L-band (1565-1625 nm). In experiment, the BFL operates in a range from 1555 nm to 1632 nm, which is the widest to the best of our knowledge. The proposed BFL is an attractive narrow linewidth laser source on the L-band, which has many potential applications, such as in slow light, coherent communication, and interferometric sensing.

Compression of chirped free femtosecond pulses in hollow core photonic bandgap fibers is investigated numerically. The results show that intrapulse stimulated Raman scattering can improve the quality of the compressed pulse. Positive third-order dispersion is the main limitation on the compression of the femtosecond pulse. However, the combined effect of the intrapulse stimulated Raman scattering and the negative third-order dispersion can form still shorter pulses than is possible with intrapulse stimulated Raman scattering alone. We also investigate the influence of width and peak power of input pulse on pulse compression.

An absolutely single polarization photonic crystal fiber (ASP-PCF) with periodic structure of sub-wavelength hole pitch is proposed. Circular air holes and elliptical air holes with diameters smaller than the operation wavelength are employed in the fiber cladding area and the fiber core area, respectively. Calculation results show that both ultra-high birefringence and ASP operation are achieved over a large wavelength range covering the fiber optical communication window from 1300 nm to 1600 nm for the proposed ASP-PCF. The ASP operation bandwidth can be further enlarged based on the optimized designs.

Double-grating coupler based on two fiber Bragg gratings(FBGs) has the advantages of compact structure and enhanced filtering efficiency. The influences of different gratings' position in the coupling region and grating length on the filtering spectra were investigated based on the unified coupled-mode theory. The results show that, the coupling region on the left of the graing mostly affects the drop channel characteristic;the length of the grating mostly affects the drop efficiency;the transmission characteristic is best with the whole length of the coupling region Lc integral multiple of coupling lengthπ /(2Kf ) .A coupler with uniform coupling region making of two photoconductive fibers was fabricated by improved fused taper technology,then two Bragg gratings were written in the coupling region with 248nm ultraviolet laser, and a grating reflecton coupler with maximum drop reflectivity 20dB and bandwidth 0.8nm was achieved.

The growth of long period fiber grating written in H2-loaded fiber within one hour immediately after fabrication was measured and analyzed. Fast deepen on difference of refraction index was obviously observed in all the experiments, but the peak wavelength to time and cross-coupling coefficient to time curves are fitted better in exponential decay function than power function, and suggest a same variation pattern in difference of refraction index.

We proposed that nanomaterials can be used to change the characteristics of standard fibers. After two stages, preform fabrication and fiber drawing, a novel inner cladding fiber with InP nano thin film has been successfully fabricated by the means of MCVD. The thickness of the InP film is about 60nm. The electric field distribution is simulated through the the finite element method. The simulation result indicates that the InP nano film can confine the electric distribution in the core. In addition, it is calculated that the effective refractive index is 1.585.

A new type BGTI with only one GTI is designed first and it could reduce PMD greatly and has much better temperature stability compared to traditional BGTI, the channel isolation rate of single-stage structure is not enough and result in crosstalk increasing and SNR reducing. To improve isolation rate, two cascaded BGTI are used to realize the second filter. Simulation and experiment results show that isolation rate is improved, the bandwidth is remained and PMD also reaches requirement design, successfully optimizing the system performance.

This paper presents a simple quantum memory method for efficient storage and retrieve of light. The technique is based on the principle of controlled reversible inhomogeneous broadening for which the information of the quantum state light is imprinted in a two-level atoms ensemble and recalled by flipping the external nonuniform electric field. In present work, the induced Stark shift varied linearly with position, and a numerical analysis for this protocol has been studied. It shows that the storage efficiency can nearly reach 100% with a large enough optical depth, and the optimal broadening for a given pulse width is also analyzed.

A Fiber Bragg Grating (FBG) sensor interrogation system using Arrayed Waveguide Gratings(AWGs) demultiplexer is designed and studied theoretically and experimentally. By using a temperature tunable arrayed waveguide grating (AWG), the center wavelength of the FBG sensor is successfully interrogated, with the linear temperature dependence of the AWG transmission wavelengths. Initial results show that the proposed wavelenght interrogation technology using AWG demultiplexer could potentially offers a low-cost, compact, and high-performance solution for the interrogation of FBG distributed sensors and multisensor arrays.

A new type fiber bending sensor based on a tilted fiber Bragg grating (TFBG) interacting with a multimode fiber (MMF) is presented. The sensing head is formed by insertion of a small section of MMF between single-mode fiber (SMF) and the TFBG. The reflection light from this sensor head includes two parts, i.e., the reflected Bragg mode and cladding modes. The latter were first coupled from the core mode to counter-propagating cladding modes by the TFBG and then coupled back into the core as a function of the MMF. The power of the cladding modes changes as the fiber is bent while the Bragg one keeps unchanged. The average reflective power in the cladding modes decreased with the increase of curvature. The measurement range of the curvature from 0m^-1 to 2.5m^-1 with a measurement sensitivity of -802.4nW/m-1 is achieved.

In this paper, a multi-wavelength fiber laser based on cascaded semiconductor optical amplifier (SOA) was proposed by using a high birefringence fiber loop mirror (Hi-Bi FLM) as wavelength filter. The 0.6nm homogeneous broadening line-width of the SOA enabled laser oscillation with WDM ITU-grid spacing possible. With this configuration, SOAs with small signal gain peak wavelengths at 1540nm and 1510nnm were cascaded as gain medium in the laser for laser oscillating in C+L band. The output results with different driving current of SOAs were obtained and compared experimentally. The wavelength spacing of this laser was controlled by using different lengths of Hi-Bi fiber. By using 5.9m Hi-Bi fiber in Hi-Bi FLM, 100GHz wavelength spacing was obtained. The output 26 wavelengths within 6dB bandwidth spacing on 100GHz were obtained. These multi-wavelengths covered C+L band and were centered on 1566.599nm. The line-width of each channel was 0.102nm with more than 25dB SNR. All these channels can be continuously tuned over 50GHz by controlling the polarization controller in Hi-Bi FLM. Output of multi-wavelength fiber laser with only one SOA as gain medium was also presented for comparison. Keywords: multi-wavelength, fiber laser, semiconductor optical amplifier, cascaded, C+L band, high birefringence fiber loop mirror, 100GHz, continuously tunable, homogenous broadening, wavelength-division multiplexing

A novel multiple-frequency Brillouin fiber-ring laser utilizing a ring cavity is proposed and experimentally demonstrated. And eight wavelengths can be obtained from this laser. Based on this laser, the mechanism for generation of high frequency microwave signal is proposed and partly realized. To confirm the feasibility of this method, 11GHz microwave signal is obtained by the experiment.

In this paper, the numerical aperture (NA) of photonic crystal fiber (PCF) is measured by a system with spectrometer, and high-precision results are obtained. The spectrometer can record the light intensity of different wavelengths. It overcomes the limitation that the traditional measurement can only measure the NA in some fixed wavelengths. We get the NA at any wavelength in 500nm~900nm range, which is determined by light source and spectrometer. Therefore, the parameters related with NA can be better studied, such as: the mode field area, cut-off wavelength and so on. The characterization of PCFs can be better represented too. The measured results are compared with theoretical calculation value, and they agree with each other very well. According to the measured NA, the mode field area of sample fiber is calculated and compared with simulation results calculated by fast-vector-method.

The deviation of cores' shape in dual-core fiber may affect the coupling characteristics between the two cores. For the same given cores' area in three kinds of dual (circular, elliptical, egg-shaped) core fiber, the relationship of the coupling length with the cores' shape is calculated at different wavelength It is found the coupling length of dual-circular-core fiber is the longest and dual-elliptical-core fiber is the shortest while dual-egg-shaped-core fiber is in the middle.

Switchable dual-wavelength fiber laser with photonic crystal fiber (PCF) Sagnac loop and broadband fiber Bragg grating (BFBG) at room temperature is demonstrated. By adjusting the polarization controller (PC) appropriately, the laser can be switched between the stable single- and dual-wavelength lasing operations by exploiting polarization hole burning (PHB) and spectral hole burning effects (SHB).

The refractive index sensor for use of mechanically induced long-period fiber grating (MLPG) in a side-hole singlemode fiber is proposed. The principle of operation is based on using of a long-period grating that is made by pressing a plate with periodic grooves against a short length of side-hole fiber. The strength of the resonant peak is tuned by adjusting the pressure applied on the side-hole SMF. The resonance wavelengths are shifted as the two side-holes of the fiber core were filled with the different the refractive index liquids. The resonant wavelength of 1588.6 nm has a total blue shift of approximately 12.2 nm for refractive index ranging from 1.35 to 1.43. The results show that it is more sensitive than that of the conventional SMF long-period fiber gratings.