A wavelength-tunable duplex integrated light source for fastwavelength switching

A new monolithically integrated opto-electronic device has been developed for fast wavelength switching in photonic packet switching. The integrated device, called a tunable duplex integrated light source comprises two distributed Bragg reflector lasers (DBR-LDs), two electroabsorption optical switches, a Y-shaped waveguide coupler, an electroabsorption modulator, and two thermal drift compensators (TDCs). The tuning range of the DBR-LDs is 3 nm, and the wavelength switching time of the optical switches is estimated to be 60 ps including a 50 ps rise time for the electrical pulse generator. The wavelength of a 10 Gb/s NRZ-modulated optical signal is switched without bit loss. Thermal crosstalk between the DBR-LDs, and wavelength drift of the DBR-LDs, which is due to a thermal transient, are effectively suppressed by thermal-drift-compensation operation using the TDCs     

Metal-defined polymeric variable optical attenuator

A variable optical attenuator (VOA) based on a metal-defined polymeric optical waveguide has been demonstrated for the first time. The metal film stressor deposited on top of the upper cladding layer not only produces the refractive index change within the core layer, but also acts as a thin-film heater allowing thermal tuning of the optical power within a metal-defined optical waveguide. Fabricated devices exhibit greater than 25 dB of optical attenuation with an applied electrical current of /spl sim/40 mA at 1550-nm wavelength. The switching speed of the VOA exhibits 800 /spl mu/s of rising and 720 /spl mu/s of falling time.     

160-Gb/s optical sampling by gain-transparent four-wave mixing in asemiconductor optical amplifier

We report on a broad-band all-optical switch that exhibits high linearity (>30 dB), high switching contrast (>25 dB), and large data wavelength tunability (100 nm). The switching principle is based on four-wave mixing. Two control pulse trains are placed in the gain wavelength region of a 1300-nm semiconductor-optical amplifier. The data signal, however, is at 1550 nm in the transparent wavelength region where four-wave mixing sidebands are generated due to index modulations. The switch is used to sample a 160-Gb/s data signal with a temporal resolution of approximately 1.7 ps     

Compact Thermally Tunable Silicon Wavelength Switch: Modeling and Characterization

A wavelength-selective photonic switch is developed based on a Si microring resonator using thermooptic effect. The 10-mum-diameter microring resonator uses single-mode strip Si waveguides of dimension 0.25 mum times 0.45 mum operating at 1.5 mum. Full-width at half-maximum are in the range 0.1-0.2 nm. The ultrawide tunable range (>6.4 nm) and wide free spectral range (~18 nm) of the switch element enables wavelength reconflgurable multichannel matrix switch by wavelength multiplexing/demultiplexing. Average rise delay time of 14 mus with low switching power of 3.15 mW has been achieved with 0.2-nm wavelength tuning and 78 mus, 104 mW for 6.4-nm tuning. Fall delay times are usually less than 10 mus. Thermal simulations show 10%-20% agreement with the measurements up to 3.2-nm tuning. The compact size of the switch shows its potential as an active element in photonic integrated circuits.     

Optical switching characteristics in Si-waveguide asymmetric Mach-Zehnder interferometer having ferro-electric liquid crystal cladding

A novel optical switching device using a Si-waveguide asymmetric Mach-Zehnder interferometer having a ferro-electric liquid crystal cladding is proposed. The switching operation was successfully demonstrated by the experimental device designed for a 1550 nm wavelength.     

Wavelength Tuning of Vertical-Cavity Surface-Emitting Lasers by an Internal Device Heater

We have fabricated thermal-induced wavelength- tunable vertical-cavity surface-emitting lasers with a 780-nm emission wavelength that is tunable by using an internal device heater. A 5.36-nm tuning range was achieved by means of a 70-mA tuning current and a 3.5-mA driving current while maintaining continuous single-mode operation and the optical power variation is less than 2.5 dB in the tuning range. In addition, a multimode tuning range of 9.1 nm was achieved with a 90-mA tuning current and a 7-mA driving current.      

Vertical coupled-cavity microinterferometer on GaAs withdeformable-membrane top mirror

Fabry-Perot microinterferometer is demonstrated that combines a GaAs-AlAs vertical cavity with a suspended movable membrane. Electrostatic displacement of the gold/silicon nitride membrane allows for broad and continuous wavelength tuning of the cavity resonance formed by the combination of the GaAs cavity and the air gap below the membrane. The device exhibits a 32-nm tuning range around the 920-nm center wavelength for 0-14 V applied bias and FWHM linewidths near 3 nm; this corresponds to membrane deflections of up to 0.27 μm. Such structures provide the foundation for wavelength selective photodiodes, light emitters, and lasers in which the active wavelength is under voltage control     

Tunable Optical Add–Drop Multiplexer Based on Silicon Photonic Wire Waveguides

A wavelength tunable optical add–drop multiplexer based on silicon photonic wire waveguides with Bragg-grating-reflectors was demonstrated by tuning the dropping wavelength through thermooptic effect. A 6.6-nm dropping wavelength shift was obtained at a 0.82-W heating power. For the device that is presently polarization-dependent, the 3-dB channel-dropping bandwidth was 0.4 nm and the extinction ratio at the dropping wavelength for port THROUGH was better than 17 dB for assuming 1.6-nm wavelength spacing dense wavelength-division multiplexing. The average tuning speed was about 200$muhboxs$.     

All-optical 1300-nm to 1550-nm wavelength conversion using cross-phase modulation in a semiconductor optical amplifier

All-optical 1300-nm to 1550-nm wavelength converters may be important components in lightwave networks which use both the 1300-nm and the 1550-nm low-loss transmission windows of silica optical fiber. We describe a new all-optical 1300-nm to 1550-nm wavelength converter, based on cross-phase modulation in a 1300-nm semiconductor optical amplifier. We demonstrate operation of the wavelength converter at 1.25 Gb/s, and present bit-error rate measurements. The wavelength converter demonstrated here potentially operates at high speed, with low input power and low polarization-sensitivity.     

All-optical wavelength conversion using a pulse reformatting optical filter

We introduce a general concept for the design of all-optical wavelength converters with pulse reformatting functionality. The novel wavelength converters are based on a single semiconductor optical amplifier followed by an optical filter. A microelectromechanical system-based realization is shown and simultaneous 40 Gb/s wavelength conversion, switching and signal format conversion is demonstrated. The new pulse reformatting optical filter device outperforms current schemes with respect to input-power requirements, input-power dynamic range and signal quality.     

Multifunctional photonic switching operation of 1500 nm Y-coupledcavity laser (YCCL) with 28 nm tuning capability

The authors present new results on extended electrical tuning, fast spatial switching, and optically controlled wavelength conversion characteristics for the recently developed InP-based Y-laser structure. The devices have a 80 nm thick bulk InGaAsP active layer and are completely grown by metalorganic vapor phase epitaxy. The facets at both ends of the chip are as-cleaved without antireflective coating. The addressable range for electrically controlled wavelength switching was extended to the record value of 28 nm. When operated as a lossless 1:2 optical space switch, fiber-to-fiber gain >0 dB, extinction ratio >50 dB and high speed operation up to 1 Gb/s were shown. Optically triggered tunable wavelength conversion including dynamic operation was also demonstrated     

Sampled grating tunable twin-guide laser diodes with over 40-nm electronic tuning range

Device and tuning characteristics of sampled grating tunable twin-guide laser diodes are presented. The vertically integrated, monolithic widely tunable laser requires only two tuning currents to fully cover a wavelength range of more than 40 nm by electrooptic tuning. Its tuning behavior is quasi-continuous with up to 8.2-nm broad continuous tuning regions. High sidemode suppression (SMSR /spl ges/ 35 dB) as well as large output power (P /spl ges/ 10 mW) are obtained over the wavelength range from 1520.5 to 1561.5 nm.     

High-power EDFA applied in distributed optical fiber Raman temperature sensor system

In this paper, a high-power erbium-doped fiber amplifier (EDFA) for the temperature sensor system is theoretically designed and experimentally demonstrated. It consists of an erbium-doped fiber that is pumped bidirectionally with two 980-nm high-power laser diodes (LDs). At the EDFA input, an optical isolator (ISO) is used to ensure that the signal pulse transmits forward only. After that, a wavelength division multiplexer (WDM) is employed to combine the forward pump laser (980 nm) and incident optical pulse (1550nm) into the erbium-doped fiber for direct amplification in the optical domain. At the EDFA output, another WDM couples the backward pump laser (980 nm) into the erbium-doped fiber and outputs the amplified optical pulse (1550 nm) with an ISO followed to isolate the backscattering light. According to this structure, we carried out the experiment in the condition as follows. For 980 nm pump LD, the operating current is 590 mA, and the setting temperature is 25℃. For EDFA, the length of erbium-doped fiber is 12.5 m, and the power of 1550 nm input signal is 1.5 mW. As a result, the power of pump LD is 330 mW, and the power uncertainty is 0.5%. The power of EDFA output at 1550 nm is 300 mW, and the power uncertainty is ±3 mW.     

Polymer micro-ring filters and modulators

Micro-ring wavelength filters and resonant modulators using polymer materials at 1300 nm and 1550 nm are analyzed, designed, and demonstrated. The rings are integrated with vertically coupled input and output waveguides. The devices are fabricated using optical lithography. Filters with a finesse of 141 and free spectral range of 5 nm at 1300 nm and finesse of 117 with a free spectral range (FSR) of 8 nm at 1550 nm are demonstrated. Ring resonators with a Q as high as 1.3 /spl times/ 10/sup 5/ at 1300 nm are demonstrated. The filters can be temperature tuned at the rate of 14 GHz//spl deg/C. Resonant ring modulators, which use an electrooptic polymer, are demonstrated. The resonance wavelength voltage tunes at the rate of 0.82 GHz/V. The modulators have a bandwidth larger than 2 GHz. Using the resonant modulator, and open eye diagram at 1 Gb/s is demonstrated.     

A novel integrated optics wavelength filter in InGaAsP-InP

An InGaAsP-InP integrated optics wavelength selective device is proposed and demonstrated. It utilizes coupling between epitaxial layers with different refractive indices and thicknesses. The device is suitable for integration to form, e.g., a monolithic receiver for wavelength division multiplexed optical communication systems. Design considerations are given. The filter bandwidth and center wavelength can be freely chosen, and bandwidths as narrow as 1.5 nm at 1.3 or 1.55 μm center wavelength are shown feasible. Electrical tuning is possible. Experimental filters show that devices can he fabricated with performance in good agreement with theory, The 22-nm -3-dB bandwidth at 1.12-μm center wavelength presently demonstrated is limited by the measurement system.     

Continuously wavelength-tunable MQW fabry-perot laser diode pulse source with a fiber-based external cavity

A simple continuously wavelength-tunable fiber ring laser pulse source is demonstrated. Such a source employs a gain-switched multiple quantum-well Fabry-Perot laser diode in a self-seeding scheme and the output pulse wavelength can be tuned continuously via a tunable optical filter. The optical pulses generated exhibit a pulsewidth of 92 ps at the frequency of 2.6 GHz. Within a wide wavelength tuning range of 46 nm, the side-mode suppression ratio and the average power of the output optical pulses obtained are higher than 50.1 dB and 3.3 dBm, respectively, and the pulse spectral stability can be maintained in the whole wavelength tuning range.     

Rapid continuous tuning of a single-polarization fiber ring laser

We have developed and studied what we believe is the first fiber laser operating in a single polarization at 1550 nm with PM fiber output and capable of wavelength tuning over a 20-nm bandwidth in less than 50 μs. The fast wavelength tuning speed in a fiber laser is achieved by incorporating an acousto-optic tunable filter into the laser. The same filter is used in an optoelectronic feedback loop to suppress the relaxation oscillations induced by wavelength transitions     

Tunable wavelength conversion in a semiconductor-fiber ring laser

A tunable wavelength converter is demonstrated using highly nondegenerate four-wave mixing in a semiconductor-fiber ring cavity with no external pump light and low input signal power requirements. This device allows continuous tuning of both pump and converted wavelengths over the semiconductor optical amplifier gain bandwidth. Results for 11.8-nm down- and 6.9-nm up-wavelength conversion with input signal power as low as -10 dBm have been obtained at 1 Gb/s with less than 1.6-dB power penalty     

All-optical pulse width and wavelength conversion at 10 Gb/s usinga nonlinear optical loop mirror

An all-optical pulse width and wavelength converter is demonstrated using a nonlinear optical loop mirror. The conversion of a 10 Gb/s, 8 ps pulse width data stream at 1551 nm to a 23 ps pulse width data stream at 1543 nm is demonstrated. The control pulse energy required for switching is 10 pJ. Bit-error-rate measurements are presented     

High-output-power polarization-insensitive semiconductor optical amplifier

A high-output-power 1550 nm polarization-insensitive semiconductor optical amplifier (SOA) was developed for use as a compact in-line optical amplifier. A very thin tensile-strained bulk structure was used for the active layer and active width-tapered spot-size converters (SSCs) were integrated on both input and output sides. The SOA module exhibited a high saturation output power of +17 dBm together with a low noise figure of 7 dB, large gain of 19 dB, and low polarization sensitivity of 0.2 dB for optical signals of 1550 nm wavelength. For the amplification of optical signals modulated at 10 Gb/s in the nonreturn-to-zero (NRZ) format, a good eye pattern without waveform distortion due to the pattern effect was obtained at an average output power of up to +12 dBm. Additionally, good amplification characteristics were demonstrated for the signal wavelength range corresponding to the C-band.