All optical switching of integrated hybrid distributed feedback bistable laser

A novel type of optical bistable circuit using both optical and electrical feedback to achieve bistable operation is reported. The circuit provides genuine optical gain, can be triggered by optical inputs over a large spectral range and minimises signal feedback to previous circuits.<>     

Fast switching bistable electromagnetic microactuator

A fast switching electromagnetic microactuator with two stable positions is presented. The actuator of size 2.0/spl times/2.2 mm is fabricated using UV-LIGA technology. Test results show that a current pulse with an amplitude of 50 mA is needed for the actuator's switching between two stable states, and the switching time is approximately 20 /spl mu/s. The displacement of the actuator is about 17 /spl mu/m.     

Fast wavelength switching and simultaneous FSK modulation using tunable DBR laser

The authors describe the operation of a tunable three-section DBR laser for multiwavelength switching with up to 48 resolvable wavelengths. Fast switching among wavelengths that are spaced over a 2.2 nm continuous tuning range and simultaneous FSK data modulation of each channel are demonstrated. A novel wide-deviation FSK modulation scheme to reduce temperature induced wavelength drifts is also described.<>     

Absorptive switching and spectral characteristics of theside-injection light-controlled bistable laser diode

Experimental results characterizing the operation of the side-injection light-controlled bistable laser diode (SILC-BLD) have been accurately modeled using simple gain expressions and rate equations. Light output versus gain section drive current has been calculated and agrees well with experiment. Further, voltage shifts (due to carrier redistribution between the gain and absorber regions) measured at switch on and off have also been modeled successfully for what is believed to be the first time in a quantum-well laser to the authors' knowledge, and agree well with experiment. Spectrally, subthreshold power-averaged wavelength versus gain section drive current measurements show a parabolic form (caused by the interplay between band filling, energy gap shrinkage, and the increase in stimulated emission). This has been successfully modeled using quantum-well gain and the associated spontaneous emission spectra, and should have wide applicability to all Fabry-Perot semiconductor lasers     

Fast switching characteristics of a widely tunable laser transmitter

We demonstrate a widely tunable laser transmitter that accesses 32 ITU channels with 100-GHz spacing and switches between all channel combinations in less than 45 ns. The compact module uses commercially available electronic components. We investigate the electrical and thermal properties of the laser and the tuning section driver. The experiments show that a low output impedance driver circuit produces faster switching times. Also, temperature variation of the laser limits the wavelength accuracy of the switching. Finally, we present the correlation between switching times and the laser tuning currents.     

Fast wavelength switching of three-section DBR lasers

For optical crossconnect and packet switched applications based on fast wavelength switching of distributed Bragg reflector (DBR) lasers, the wavelength switching delay is an important device characteristic. A large-signal model for a three-section DBR laser is described which permits evaluation of the intramodal and intermodal wavelength switching delay. The steady-state mode spectrum and loss obtained from a transmission line model of the laser are used in modified multimode rate equations to explicitly include the device structure and operating conditions in the dynamic model. Mode competition is shown to cause the intermodal wavelength switching delay to increase significantly as the destination wavelength approaches the edge of a mode tuning curve. The same behaviour is observed experimentally     

Fast tunable wavelength conversion for all-optical packet switching

We demonstrate a simple scheme to achieve fast tunable wavelength conversion over a wide spectral range. The wavelength conversion is obtained by four-wave mixing in a semiconductor optical amplifier using a double-pump scheme, 2048-bit sequences at 2.5 Gb/s, incoming at a given wavelength, are alternatively converted toward two different wavelengths for a total conversion interval of 20 nm. With this method, the time needed to change the destination wavelength is much shorter than the bit duration. This feature makes any guard-time spacing between packets unnecessary. Bit-error-rate measurements show that the process occurs with negligible penalties (less than 0.3 dB).     

A new bistable laser diode configuration for all optical switching

A new bistable laser diode configuration for all optical switching has been suggested and its equivalent circuit model is developed. For switching the device to the high state (set) a TE mode optical pulse is required, which is the oscillating mode of the laser, whereas a TM mode pulse is used to bring the output to a low state (reset). But the wavelength of the set and reset pulses are the same as that of the lasing wavelength of the device. The static and dynamic characteristics are studied by simulating the equivalent circuit model using the circuit simulation program PSPICE. It is found that as the carrier lifetime τ_a of the absorption section increases, the width of the optical pulse required for reset increases nonlinearly. The rise and fall times are found to be 0.15 and 0.16 ns, respectively, for a τ _a, of 3 ns     

光纤布拉格光栅非线性双稳开关特性研究

采用数值模拟的方法研究了光纤布拉格光栅(FBG)的非线性双稳开关特性.从耦合模理论出发,利用Jacobi椭圆函数法得到了3种不同的解,首先对3种解下的非线性双稳开关特性分别进行比较,然后针对各个解下的影响开关特性的失谐量、耦合系数和光栅长度等参数进行分析,研究结果对于分析和构建非线性双稳FBG光开关具有一定的意义.     

Optical switching characteristics of a bistable resonant tunnelling light emitting diode

The electrical and optical characteristics of a bistable resonant tunnelling light emitting diode are reported. The maximum frequency of operation is determined by electron tunnelling escape rather than by radiative recombination. Switching time constants of less than 200 ps are measured, limited by the duration of the electrical excitation.<>     

Actively modelocked, quadruple-wavelength fibre laser with pump-controlled wavelength switching

An actively modelocked quadruple-wavelength erbium-doped fibre laser with two wavelengths in each of the C- and L-bands (with wavelength spacings of 3.5 nm and 0.4 nm, respectively) is reported. The pulse durations are 50-55 ps with corresponding time-bandwidth products of 0.48-0.63. By simple adjustment of the pump power, the laser can be switched to emit at any combination of the 4 wavelengths, without changing the repetition rate of the output pulses.     

Less than 5-ns wavelength switching with an SG-DBR laser

We achieve fast wavelength switching between all channel combinations of a 64-channel sampled-grating distributed Bragg reflector laser in less than 5 ns. The laser was designed to have low tuning currents and efficient heat extraction in order to reduce parasitic thermal effects. We also report on the behavior of the front and back mirror pre-emphasis amplitudes required for the fast switching.     

Picosecond switching dynamics of a bistable-wavelength-latchtwo-segment distributed feedback laser

The bistable-wavelength-latch operation of a two-segment distributed-feedback laser was observed and characterized. Short electrical trigger pulses were used to demonstrate mode power switching in less than 200 ps with only 450-ps delay between set and reset pulses. Spectrally resolved measurements show transient spectral broadening during the bistable wavelength switching. Fast laser wavelength switching is important for wavelength-division-multiplex photonic switching systems     

双稳外腔半导体激光器(ECLD)模式转换的数值描述

对多模半导体激光器(LD)的速率方程组进行了数值求解,分析了光栅双稳外腔半导体激光器(ECLD)模式发生跳变时的瞬态特性,讨论了光栅转角的大小对瞬态过程的影响。结果表明,当光栅转角较小时,ECLD在功率上跳过程中,切断模(switch offmode)在熄灭前可能会产生一个窄而强的光脉冲。这一现象在下跳过程中是不存在的。且上跳时,ECLD更快地达到稳态输出。     

Simultaneous fast wavelength switching and intensity modulationusing a tunable DBR laser

The use of a three-section distributed Bragg reflector (DBR) laser to switch wavelengths rapidly and simultaneously transmit data by intensity modulation is discussed. This combination simulates the operation of a tunable transmitter in a multiwavelength packet switch. In this type of switch, each output port is tuned to receive data on a unique, fixed wavelength; packets are routed from input ports to the appropriate output ports by wavelength addressing. In each transmission cycle, the input port transmitter tunes to the wavelength associated with the intended output port and subsequently broadcasts the data packet. Limitations on various system parameters, such as the number of allowed channels, the wavelength switching times, and packet lengths (residency times), as determined by thermally-induced wavelength drifts are also discussed. The advantages of using a single device for both fast wavelength switching and direct data modulation are significant: the elimination of external modulators improves both the simplicity of the implementation and the available power budget     

19 ps switching of a bistable laser diode with 30 fJ optical pulses

19-ps optical switch-on of a bistable laser diode with only 30-fJ input coupled optical energy at a repetition rate of 500 MHz is reported. The bistable laser was an inhomogeneously pumped three-section Fabry-Periot laser diode. The switch-off time was 94 ps, probably limited by the duration of the electrical reset pulse. Longer turn-on delay times were recorded when switching with less input energy     

Chaos in wavelength of tunable semiconductor laser diode with time-delayed Fabry-Perot feedback

With time-delayed Fabry-Perot feedback, chaos in the wavelength of a tunable semiconductor laser diode has been successfully demonstrated. The nonlinear feedback function can be easily tuned by varying the optical path difference of a Fabry-Perot cavity. Experimental results are compared with theoretical simulation and good agreement is obtained.     

Femtojoule bistable optical switching of inhomogeneously pumped laser diode at 500 MHz using mode-locked tunable diode laser

The authors have investigated the nonlinear transfer characteristics and temporal response of bistable three-section lasers within a broad wavelength interval (30 nm), when switched with picosecond optical pulses (20 ps) at a high repetition rate. The minimum input coupled switch-on energy was 0.7 fJ. The shortest switching time was 60 ps.<>     

Fast method for accurate prediction of fibre laser oscillation wavelength

An accurate and simple laser model, which includes the detailed spectral shape of the emission and absorption cross-sections, is suggested and investigated.<>     

New 1.5 ?m wavelength GaInAsp/InP distributed feedback laser

A new 1.5 ?m-wavelength GalnAsP/InP distributed feedback buried-heterostructure laser was fabricated by a three-step LPE growth process. The second-order corrugation grating was formed on the waveguide layer grown on the active layer. High differential quantum efficiency of 13%/facet was obtained. Single-longitudinal-mode operation in the temperature range from ?20°C to 55°C was obtained.