With reference to the IEC 60793-1-140 international standard of optical fibre measurement methods and test procedures in attenuation, we studied the optical fibre attenuation measurement by cut-back method using tuneable lasers source. By using a power stabilised laser source, we measured the fibre attenuation in the wavelength range from 1270 nm to 1350nm and from 1520 nm to 1620 nm using ‘cut-back’ technique. The power measurement before and after cut-back have better repeatability. Besides, the evaluation of the splicing losses before and after cut-back as well as the evaluation of effective refractive index (Neff) will improve the accuracy in calculating the fibre attenuation. Our method will improve accuracy and reduce uncertainties in the measurement and thus enable us to establish our own optical fibre spectral attenuation standard.
A novel few-mode fiber based sensor for monitoring the vital signs of pulse (heart rate), and breathing rate (respiratory rate) was developed. The sensor was applied in non-invasive measurement of pulse and breathing rates. The pulse, breathing and even body movement affected the sensor’s output as the strain on the few-mode fiber changed with these activities. This sensor has simple structure and easy to fabricate. Its signal is easy to monitor. It can be used in the medical equipment in what situation non-invasive realtime monitoring and measurement of pulse rate, and respiratory/body movement pattern of healthy subjects are required.
A fiber optics based 1310nm laser was applied with the primary standard cryogenic radiometer for optical power measurement to extend NMC’s spectral responsivity scale toward infrared wavelength. The absolute optical power was measured and two absolute transfer standard detectors (InGaAs based trap detectors) were calibrated at 1310nm. The measurement setup is described and the measurement uncertainty was analyzed. The advantages of using fiber optics based laser sources are discussed in the paper. With the new calibration capability, the uncertainty of the spectral responsivity in the range from 900nm to 1640nm in NMC will be improved.
Series coupled triple ring resonators are designed and fabricated on a SOI platform as a thermo-optic wavelength selective switch (TO-WSS) having individual ring resonance tunability and narrow band, flat-top spectrum with high channel isolation. Optimal detuning combinations of the ring resonators are identified in the WSS to achieve an effective OFF state with high channel extinction, low switching cross talk, and low loss of OFF state. It is observed that detuned OFF states with a single ring which is adjacent to the input bus waveguide and two rings which are adjacent to the drop waveguide, are more effective for the highest channel extinction, lowest switching cross talk, and zero loss of OFF state in the WSS. A maximum channel extinction of 22 dB, lowest switching cross talk of −30 dB, and a zero loss of OFF state is achieved with a single ring detuned OFF state using a switching power of 48 mW.
Silicon Photonics taps on the volume manufacturing capability of traditional silicon manufacturing techniques, to
provide dramatic cost reduction for various application domains employing optical communications technology. In
addition, an important new application domain would be the implementation of high bandwidth optical interconnects in
and around CPUs. Besides volume manufacturability, Silicon Photonics also allows the monolithic integration of
multiple optical components on the same wafer to realize highly compact photonic integrated circuits (PICs), in which
functional complexity can be increased for little additional cost. An important pre-requisite for Si PICs is a device library
in which the devices are compatibly developed around a common SOI platform. A device library comprising passive and
active components was built, which includes light guiding components, wavelength-division-multiplexing (WDM)
components, switches, carrier-based Si modulators and electro-absorption based Ge/Si modulators, Ge/Si photodiodes
and avalanche photodiodes, as well as light emitting devices. By integrating various library devices, PIC test vehicles
such as monolithic PON transceivers and DWDM receivers have been demonstrated. A challenge with Si PICs lies with
the coupling of light into and out of the sub-micrometer Si waveguides. The mode size mismatch of optical fibers and Si
waveguides was addressed by developing a monolithically integrated multi-stage mode converter which offers low loss
together with relaxed fiber-to-waveguide alignment tolerances. An active assembly platform using MEMS technology
was also developed to actively align and focus light from bonded lasers into waveguides.
This paper illustrates the design and fabrication of wavelength filters using resonant cavity which is constructed out of a
phase shifted vertical side wall grating. The resonant cavity is analyzed as a Fabry-Perot resonator and the variation in
cavity quality factor (Q) and transmission with respect to various grating parameters is studied. It is observed that a high
Q-factor together with a high transmittivity can be obtained for this wavelength filter through optimization in grating
length and reduction in the out of plane loss. Multiple phase shifts are applied in the grating to get a coupled cavity
configuration so that channel isolation and spectral shape is improved. The channel wavelengths in a DWDM ITU grid
C band (100GHz spacing) is simulated by varying the phase shift length of the gratings and good channel isolation
with constant Q -factor and transmittivity is observed for the spectrum. The paper also explains the effective fabrication
process flow for this structure on a silicon wafer through e-beam lithography and Reactive Ion Etching (RIE).
This work presents a thermal analysis that explains experimental observation in all-optical magnetic recording (AOMR).
An integrated model is used to describe thermal processes at different time scales in AOMR. The formation of magnetic
marks is discussed and implemented by developing a simulator based on 3-dimensional finite element method (FEM).
The simulator is able to carry out thermal analysis of the thin film media and is a useful tool for design of AOMR media
structure, especially for the thermal sink layer.
We propose a new passive optical network (PON) configuration and a novel silicon photonic transceiver architecture for optical network unit (ONU), eliminating the need
for an internal laser source in ONU. We adopt dual fiber network configuration. The internal
light source in each of the ONUs is eliminated. Instead, an extra seed laser source in the
optical line termination (OLT) operates in continuous wave mode to serve the ONUs in the
PON as a shared and centralized laser source. λ1 from OLT Tx and λ2 from the seed laser are
combined by using a WDM combiner and connected to serve the multiple ONUs through the
downstream fibers. The ONUs receive the data in λ1. Meanwhile, the ONUs encode and
transmit data in λ2, which are sent back to OLT.
The monolithic ONU transceiver contains a wavelength-division-multiplexing (WDM) filter
component, a silicon modulator and a Ge photo-detector. The WDM in ONU selectively
guides λ1 to the Ge-PD where the data in λ1 are detected and converted to electrical signals,
and λ2 to the transmitter where the light is modulated by upstream data. The modulated
optical signals in λ2 from ONUs are connected back to OLT through upstream fibers.
The monolithic ONU transceiver chip size is only 2mm by 4mm. The crosstalk between the
Tx and Rx is measured to be less than -20dB. The transceiver chip is integrated on a SFP+
transceiver board. Both Tx and Rx demonstrated data rate capabilities of up to 10Gbps. By
implementing this scheme, the ONU transceiver size can be significantly reduced and the
assembly processes will be greatly simplified. The results demonstrate the feasibility of mass
manufacturing monolithic silicon ONU transceivers via low cost
Mode-evolution-based polarization rotators in silicon waveguides were studied. The rotator's performance
was studied under normal and abnormal launching conditions. The rotator with minimum length of 40μm was
demonstrated to provide the polarization rotation with polarization extinction ratio of 15dB at abnormal launching
condition. The insertion loss at the transition region was less than 1dB.
Recent developments in the short distance communication have made polymer optical fibers (POF) an attractive product
in the high speed data communication market. The requirement of a large bandwidth, low cost, light weight and
flexibility in installation have placed them over the copper cables especially in applications like home networking and
automotives. Since POFs are large core multimoded fibers, their band width is limited by intermodal dispersion. This
confines POFs application to low data rate short distance communications. Restrictive mode launchers (RML) and
higher order mode strippers placed in the data link helps to reduce the intermodal dispersion. The techniques used to
implement these signal conditioners should be simple and cost effective to keep POFs attractive in the short distance
communication. In this paper we explore the possibility of integrating the RML and mode stripping elements in the
transmitter and receiver package itself. The pre-designed optical signal conditioning elements are projected to get
molded in the plastic packages and are fiber plug in modules. This connector less package design, universal to any light
source proposes to enhance the data rate and is widely manufacturable at an ease of installation and low cost.
There is an increasing demand for tunable lasers in telecommunications networks for test equipment, optical components
and other applications. In DWDM systems, multiple data streams propagate concurrently on a single mode fiber.
DWDM networks are based on a DFB lasers operating at a wavelength defined by ITU wavelength grid. Statistical
variations associated with the manufacture of DFB laser results in yield losses. Continuously tunable external lasers are
developed to overcome the limitations of DFB lasers. Various laser tuning mechanisms are being explored to provide
external cavity tunable lasers to provide a stable single mode output.
The packaged tunable laser source (TLS) for DWDM network also need to include several optical elements for isolation
and data modulation like collimator, focusing lens, fiber pigtail, a modulator and output fiber segment. In this
publication, we propose a novel semi integrated miniature high frequency tunable laser design based on Silicon Optical
Bench (SiOB) concept. One of the mirrors is a movable MEMS structure changing the optical path length. We propose
micro optical design between laser diode and the MEMS mirror for efficient optical coupling and side mode suppression.
We also present the compatibility between the optical coupling and MEMS actuation range. We present the coupling
efficiency results over the tuning range. We also propose a method of monitoring the output power of the tunable laser
using waveguide coupler structures which are integrated in the silicon wafer and method of packaging in a miniature
package compatible to the industry standard form factor.
Polymer Optical Fiber (POF) optical modules are gaining momentum due to their applications in short distance
communications. POFs offer more flexibility for plug and play applications and provide cost advantages. They also offer
significant weight advantage in automotive and avionic networks. One of the most interesting field of application is
home networking. Low cost optical components are required, since cost is a major concern in local and home networks.
In this publication, a fast and easy to install, low cost solution for efficient light coupling in and out of Step Index- POF
is explored. The efficient coupling of light from a large core POF to a small area detector is the major challenge faced.
We simulated direct coupling, lens coupling and bend losses for step index POF using ZEMAXR optical simulation
software. Simulations show that a lensed fiber tip particularly at the receiver side improves the coupling efficiency. The
design is optimized for 85% coupling efficiency and explored the low cost fabrication method to implement it in the
system level. The two methods followed for lens fabrication is described here in detail. The fabricated fiber lenses are
characterized using a beam analyzer. The fabrication process was reiterated to optimize the lens performance. It is
observed that, the fabricated lenses converge the POF output spot size by one fourth, there by enabling a higher coupling
efficiency. This low cost method proves to be highly efficient and effective optical coupling scheme in POF
communications.
In this study, a low-cost (with bare chips) and high (optical, electrical, and thermal) performance optoelectronic system with
a data rate of 10Gbps is designed and analyzed. This system consists of a rigid printed circuit board (PCB) made of FR4
material with an optical polymer waveguide, a vertical cavity surface emitted laser (VCSEL), a driver chip, a 16:1 serializer,
a photo-diode detector, a Trans-Impedance Amplifier (TIA), a 1:16 deserializer, and heat spreaders. The bare VCSEL, driver
chip, and serializer chip are stacked with wire bonds and then solder jointed on one end of the optical polymer waveguide on
the PCB via Cu posts. Similarly, the bare photo-diode detector, TIA chip, and deserializer chip are stacked with wire bonds
and then solder jointed on the other end of the waveguide on the PCB via Cu posts. Because the devices in the 3D stacking
system are made with different materials, the stresses due to the thermal expansion mismatch among various parts of the
system are determined.
The high cost of optoelectronics components typically used for long-haul communication is prohibitive in the Fiber to
the Home (FTTH) and Passive Optical Networks (PONs). One method of cost reduction is through the reducing the cost
of the electronics in the transceiver and reducing the packaging cost. We report the development of low-cost 2.5-Gbps
optical transceiver for Gigabit Passive Optical Network (GPON) using CMOS driver ICs and chip-on-board assembly
method. We developed the Laser Diode Driver (LDD), Trans-impedance Amplifier (TIA), Limiting Amplifier (LA) and
the Clock and Data Recovery (CDR) using CMOS technology for short reach application and developed the burst mode
version of the ICs for PON applications. The ICs are designed in house and fabricated on a standard CMOS 8" wafer
with 0.18μm technology. The devices operate at 1.8V and are low power in nature, thus reducing the demand on power
dissipation. The transceiver consists of an un-cooled and direct modulated laser diode driven with a LDD, a high speed
PIN photo-diode with amplifier and CMOS ICs. The bare CMOS ICs are attached on a transceiver substrate that is
compliant with the small form-factor pluggable (SFP) package multisource agreement (MSA) and coupled to a 1310nm
FP laser TOSA and a PIN ROSA with LC connector. The integrated transceiver is characterized up to 2.5-Gbps. In this
publication, we present the detail of the module development, assembly methods and performance characterization at
1310nm.
A taper coupler with multimode input and single mode output is presented for coupling between edge emitting laser
diode and silicon waveguide. The tapered coupler structure is optimized and tolerance for laser diode placement is
studied. A typical coupling efficiency of -2dB is achieved from laser diode to silicon waveguide. With tolerance of +/-
4μm laterally or vertically, the variation of the coupling efficiency is about 3dB. The tolerance is large compared with
other methods. Tilting angle at laser diode and the small gap between tapered coupler and silicon waveguide also affect
the overall coupling. From our studies, horizontal and vertical offsets are more critical for laser diode placement in order
to have a good coupling. The new design can be applied to photonics packaging because it will make passive assembly
easier by having larger tolerance for packaging compared with the conventional method with lens.
A new method of coupling the light from a laser diode to a Single Mode Fiber (SMF) with large alignment tolerances
and without using coupling lenses is presented. A pseudo vertical tapered coupler is designed for light coupling between
laser diode and single mode fiber. It has a large input aperture which is about 100 times the size of the laser waveguide
cross-section. The tapered coupler provides single mode output and matches the mode size with the single mode fiber.
The tapered coupler is fabricated on a silicon optical bench and is located between the laser and the fiber through the
silicon micrfabrication process. The misalignment between the fiber and taper coupler can be very small since this is
controlled by high precision silicon optical bench patterning processes. The coupler relaxes the laser diode placement
accuracies and eliminates the need for a coupling lens. Design Studies showed that the tolerance between the laser diode
and taper coupler can be more than +/-5μm misalignment at x-y, and +/-0.5degree tilting angle tolerance and the
fabricated assembly results are encouraging with good placement tolerances and coupling efficiency. The laser to single
mode fiber coupling tolerances is greatly improved and passive alignment for laser and single mode fiber is realized. The
technology can be useful for multi channel optical assembly where significant device and process cost saving can be
achieved and is suitable for functional integration for silicon photonics.
A compact wavelength division multiplexing (WDM) module is designed using discrete micro optics
components assembled on silicon optical bench for multiple-channel transceivers. This design is optimized
for a 4-channel multiplexer (MUX) plus a 4-channel demultiplexer (DEMUX). In this design, the micro
optics components for the MUX and DEMUX are integrated, and the MUX and DEMUX share the same
space. This helps to minimize the number of components required and hence reduce the cost and size.
Therefore, the module is compact enough to be put in small standard packages (SFF/SFP).
We develop a new model to simulate and analyze sidelobes' influence on the pulses characteristics and performance of
fiber Bragg grating-based Q-switched fiber laser. Our simulation results show that uniform fiber Bragg gratings with
sidelobes negatively affect the Q-switched fiber laser performance. Their sidelobes introduce undesired multi-peaks and
decrease the output pulses energy, while the apodized fiber Bragg grating with high sidelobe-suppression-ratio is able to
eliminate the multi-peaks effectively and generate higher energy pulses with smoother profile. Experimental work has
been conducted to validate the proposed model and verify the simulation results.
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