Gao Zhi Xiao

Arrayed-waveguide-grating-based interrogator for wavelength-modulated multi-fiber-optic sensor applications

Simultaneous interrogation of six distributed wavelength modulated fiber-optic sensors has been demonstrated using an arrayed-waveguide-grating-based interrogation technique proposed by our laboratory. This letter analyzes the operating principle of the method and reports the experimental results of this application. The results show that the interrogator proposed offers better than 1-pm wavelength resolution and has the potential of being packaged into a hand-held rugged device.

Planar waveguide-based silica–polymer hybrid variable optical attenuator and its associated polymers

We have proposed a silica-polymer hybrid variable optical attenuator that we made by creating two trenches along the core of a straight silica planar waveguide and filling the trenches with a polymer. The polymer, which had a superhigh thermo-optic coefficient, was specially designed and developed in this study to lower the power consumption of the device. We achieved a maximum attenuation of -29 dB for the device by changing the polymers temperature by only 7 degrees C. The device has a very low power consumption at 2-3 mW/channel, making it a good candidate for integration with arrayed waveguide gratings.

Active alignment of optical fibers to planar waveguides using a thermal-curing adhesive

This paper described a process that was developed for the active alignment of optical fibers to planar waveguides using a thermal-curing adhesive, in order to improve the performance and reliability of waveguide-based components. The process combines alignment at a temperature selected for adhesive curing with offline postthermal treatment of the aligned device that is suitable for volume manufacturing. A specially designed fiber-array holder and a waveguide-device holder were used to overcome the effects of temperature and stress on the alignment, simplifying the alignment from high temperature to room temperature. By studying the adhesive curing kinetics and the buildup of adhesive bonding strength, the alignment was tuned to balance performance and efficiency. Using this alignment process, fiber-to-waveguide couplings that provide low optical loss, strong bonding, and excellent reliability were achieved.

Effects of environment temperature induced heater resistance change on the attenuation of MZI type variable optical attenuators

Effects of environment temperature induced heater resistance change on the performance of Mach-Zehnder interference type variable optical attenuators (VOA) were described in this letter. To predict the heater effect, a simple model was proposed. It was found that the heater effect accounted for a large part of the thermal instability of the VOA device studied.

A cost-effective solution for packaging the arrayed waveguide grating (AWG) photonic components

Precision laser machining technology was used to cut arrayed waveguide grating (AWG) devices from 6-in wafers by following their complex profiles in a fully automatic way. A substantial cost saving in components manufacturing was achieved by an obtained device-cutting yield of 100%. The profile-cut AWG devices have smooth cutting edges and their optical performances were found unaffected by the cutting. These devices were processed in the subsequent packaging process easily without adding cost. They were proven mechanically stable in their packaging in meeting the telecommunication standards even though they have irregular geometry.

A stress-free packaging solution for planar waveguide-based photonic components

It is a challenge to simultaneously prevent the fiber ribbons from internal stress in the planar waveguide-based components and protect the ribbons from external stress. We have achieved this by simply incorporating two soft elastomer gaskets into each conventional packaging to compensate the mismatched thermal expansion between the fiber ribbon and packaging case, and fastening the fiber ribbon to the case to transfer their external load away. The involved process was easily implemented at a minimum cost, and the packaged variable optical attenuators and arrayed waveguide gratings were free of internal ribbon stress and able to meet the fiber-handling requirement as specified by Telcordia GR 1209 test.

Novel polarization scrambling OSNR monitor

A novel polarization scrambling optical signal-to-noise ratio (OSNR) monitor has been proposed and demonstrated. The OSNR monitor consists of a polarization scrambler, a polarizer and a photodetector. When the channel signal input to the polarizer is a linear polarization state aligned parallel (orthogonal) to the polarizer the output reaches its maximum (minimum). The OSNR can be obtained from the measured maximum and minimum of the output power if the sampling time is long enough to ensure a good coverage on Poincare sphere. The effects of polarizer extinction ratio and sampling time on the accuracy have been discussed.

A simple channel gain equalizer design using an arrayed waveguide gratings based demultiplexer

Using an arrayed waveguide gratings (AWG) based demultiplexer, a simple channel gain equalizer can be designed. The gain equalization and blocking functions are realized by the hybrid waveguide based variable optical attenuators fabricated on the output waveguides of the demultiplexer. This paper discusses the operation principle of the design and presents some simulation results.

Simultaneously Interrogation of Multi Fiber Bragg Grating Sensors by an AWG Based Demultiplexer

Multifiber Bragg grating (FBG) sensor arrays are being used in the health monitoring of aerospace structures and civil engineering works, as well as the environment monitoring. However, the field interrogations of multi FBG sensors are still a big challenge due to the lack of portable, robust, high performance multi sensor interrogation devices. We have found that by thermally scanning an arrayed waveguide gratings (AWG) based demultiplexer, a device deployed in the telecommunication networks, multi FBG sensors can be precisely monitored simultaneously. The measurement resolution of this technique can be better than one picometer (equivalent to 0.1degC for temperature sensing) and the measurement time can be as short as milliseconds. Owning to the small size and ruggedness of AWG, it is potentially feasible to fabricate an all solid (no moving parts), palm size, robust and high-resolution interrogator for multi FBG sensor applications

Widely tunable triple-wavelength erbium-doped fiber ring laser and its applications

We have developed a widely tunable, narrow-linewidth, simultaneous triple-wavelength oscillation erbium-doped fiber ring laser (EDFRL), which can produce double-wavelength oscillations with the same polarization output, as well as another widely tunable wavelength oscillation with orthogonal polarization from 1522.2 nm to 1595.9 nm. By using this EDFRL along with a method of measuring polarization-mode dispersion (PMD) in optical fibers based on a broad-band orthogonal-pump four-wave mixing in a semiconductor optical amplifier (SOA), we have measured the PMD values of optical fibers, which are in good agreement with values measured by means of commercial PMD testing equipment. We have also proposed several novel devices for in-field PMD measurement and monitoring on dense wavelength-division multiplexed (DWDM) traffic-carrying links, which will significantly reduce the cost and time of the PMD testing in the running DWMD networking systems.