We experimentally demonstrate a 8×8, 200 GHz cyclic AWG router using silicon oxynitride waveguides. The relative refractive index difference between the core and cladding layers is 9.75%. The output spectral response when light of TM polarization is input from the central input channel shows the central channel loss, non-uniformity and crosstalk are -1.51 dB, 2.23 dB, and -19 dB, respectively. And when light is input from the edge input channel, the central channel loss, non-uniformity and crosstalk are -3.68 dB, 2.38 dB, and -19 dB, respectively. Crosstalks vary from -19 dB to -21 dB for all channels. The device is polarization sensitive and a polarization dependent wavelength shift occurs in the spectral response of each output channel. The central wavelengths from central input channel to central output channel for the TE and TM polarization are 1553.8 nm and 1550.2 nm.
In this paper, a ratiometric wavelength monitor at around 1550 nm based on the passive Silicon-on-Insulator (SOI) integrated device is proposed, theoretically investigated and fabricated. This monitor is made of a single Mach-Zehnder Interferometer (MZI) with direction coupler acting as edge filter. The ouput spectral response is designed to be ‘X-type’. The device shows a resolution of better than 0.4 nm over the wavelength range from 1505 nm to 1585 nm with a discrimination range of 30.5 dB from 15.5 dB to -15dB, which is suitable for wavelength measurement. Based on the single mode principle, the waveguide has a 220 nm×500 nm cross section for TM-polarized mode, and the total chip size is only 18 um×20 um. In conclusion, this proposed ratiometric wavelength monitor based on a single Mach-Zehnder Interferometer on SOI platform can realize the excellent resolution over large wavelength range.
KEYWORDS: Polarization maintaining fibers, Sensors, Temperature metrology, Refractive index, Fiber optics sensors, Single mode fibers, Biological and chemical sensing
A polarization-maintaining fiber (PMF) sensor for simultaneous measurement of the temperature and refractive index (RI) based on the Mach–Zehnder interferometer is proposed and demonstrated experimentally. This fiber sensor is constructed by sandwiching a 20-mm waist-enlarged PMF between two single-mode fibers (SMFs). Using the wavelength shifts of different interference dips and the sensitivity matrix, two external parameters can be measured simultaneously. Experiment results show that the sensitivities to the temperature are 145.6 pm/°C and 0.1256 nm/°C and the sensitivities to the RI are −35.0502 and −23.3694 nm/RIU for two interference dips, respectively. This fiber sensor is simple and easy to fabricate, has high sensitivity, and can be applied to other fields, such as biological and chemical sensings.
A novel method for designing a silica waveguide based visible etched diffraction grating (EDG) with uniform loss is proposed. The designed 1st-order EDG comprises 121 output waveguides with a 2.5 nm channel spacing at a wavelength range from 400 nm to 700 nm. Using the conventional flat-field design with two-stigmatic-points method, the simulated channel loss non-uniformity of a conventional EDG is 2.66 dB. By changing the central output waveguide position and rotating the angles of grating facets according to an appropriately designed distribution function, the loss non-uniformity is reduced to 1.36 dB and the highest loss of marginal channels is decreased from 2.69 dB to 2.13 dB simultaneously. With a total chip size of 30 mm×16 mm, this visible EDG is suitable for realization of spectrometer-on-chip. The proposed design method can achieve insertion loss uniformity in a wide wavelength range with no additional element or extra fabrication step.
A compact silicon arrayed waveguide grating router (AWGR) for optical interconnects is experimentally demonstrated.
The design, fabrication and characterization of this 4×4 AWGR with a 1250 GHz channel spacing and a 5 THz free
spectral range are discussed. The loss of the AWGR varies from 2.5 dB to 5.5 dB and the crosstalk is better than -18 dB.
The functionality of the AWG as a router and its good rotation property are also presented. This device has a compact
footprint of 0.46×0.26mm2.
We report that the end facet of an optical fiber can be coated with polyelectrolyte multilayers (PEM) of polycation (diallyldimethyl ammonium chloride) and polyanion (styrenesulfonate sodium salt) (PDDA+PSS)n (n is the number of bilayers), which functions effectively as a Fresnel-reflection based biosensor. The experimental setup includes a broadband light source, a 3dB coupler, and an optical spectrum analyzer. Biotin and streptavidin are deposited onto the multilayers-coated end facet sequentially. The light intensity change due to variation of external refractive index is monitored. When the concentrations of streptavidin changes from 0.1mg/ml to 1mg/ml, a linear relationship between the concentration of streptavidin and the reflected optical power at the wavelength of 1530nm is observed. The sensitivity increases from -1.6262×10-3 dB/ppm to -4.7852 ×10-3 dB/ppm, when the number of PEM increases from 1 to 2. Then we confirm the optimized numbers of bilayers of PEM are 5 through experiment. Selectivity and repeatability of our proposed optical fiber biosensor are verified. When bovine serum albumin (BSA) is added instead of streptavidin, the obtained spectra overlaps with that of biotin’s. The final end facet coated with PEM and biotin-streptavidin can be cleaned using microwave vibration or aqua regia. The microwave vibration method is utilized due to security concern. The optical spectra changes back to the initial one of the optical fiber in air. In conclusion, a Fresnel-reflection based optical fiber biosensor with good sensitivity, selectivity and repeatability is proposed. This biosensor has the advantages of simple structure, low cost and reliability.
In this paper we review our work on birefringence compensated arrayed waveguide grating. We elaborate on a
birefringence compensation technique based on angled star couplers in arrayed waveguide grating (AWG) and discuss
several demonstrations both in low-index-contrast and high-index-contrast material systems. A 16-channel AWG with
100GHz channel spacing for DWDM application is designed and fabricated in silica-based low-index-contrast
waveguide. The experimental results confirm that the polarization-dependent wavelength shift (PDλ) can be tuned by
varying the incident/diffraction angle at the star couplers and a birefringence-free property can be achieved without
additional fabrication process as compared to conventional AWG. A further validation of this technique is demonstrated
in high-index-contrast silicon-on-insulator waveguide, in combination with different diffraction orders for TE and TM
polarizations. A birefringence compensated silicon nanowire AWG for CWDM optical interconnects is designed and
fabricated. The theoretical and experimental results show that the PDλ can be reduced from 380–420nm to 0.5–3.5 nm,
below 25% of the 3 dB bandwidth of the channel response in the wavelength range of 1500 to 1600nm.
The design and simulation results of temperature-insensitive arrayed waveguide gratings based on silicon nanowires are presented.
The temperature dependent wavelength shift is minimized by using negative thermo-optic coefficient material SU-8 as the
upper-cladding. Simulation results show that by using an appropriate thickness and width of the waveguide, quasi-athermal
operation can be achieved. For temperature varying from 0°C to 80°C, the TD-CWS can be controlled down to 0.036nm with
little polarization dependence for 272nm×253nm waveguide.
Stress-induced birefringence in silica-on-silicon waveguides is analyzed by the finite element method using the
normalized plane strain model. The simulation results show that the thermal expansion coefficient of the upper-cladding
is the most critical factor. A waveguide with zero birefringence is obtained and used to realize polarization independent
AWGs.
KEYWORDS: Waveguides, Fiber to the x, Single mode fibers, Plasma enhanced chemical vapor deposition, Receivers, Refractive index, Transmitters, Beam propagation method, Photomasks, Analog electronics
A low-loss broadband Y-branch for fiber-to-the-home applications is presented. Smaller waveguide height is utilized for
the potential of better deposition of the upper-cladding. A multimode section allows broadband operation. Simulation
results show good performance in the wavelength region from 1200nm to 1700nm for FTTH systems.
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