All-optical bit-pattern matching with photonic switching arrays

An all-optical XOR logic circuit is demonstrated using photonic switching arrays that integrate multiple-quantum-well reflection modulators and phototransistors. The switching element performs a Boolean logic A B operation on two binary input light signals that are separately incident on the phototransistor and modulator. The XOR logic function is derived by optical coupling of the switching elements. The device features high contrast that enables high-speed bit pattern matching in parallel     

All-optical switching with low-peak power in microfabricated AlGaAswaveguides

We report all-optical switching with low-peak power in a microfabricated AlGaAs waveguide operating at 1.6 μm. We show that by using a 1-μm long microfabricated strongly-guided waveguide with 0.8 μm by 0.9 μm mode cross-sectional area, switching is achieved with an average power of 1.2 mW for 82-MHz mode-locked 430 fs pulses. The estimated peak pump power and pulse energy inside the microfabricated waveguide were ~30 W and ~14.6 pJ, respectively, which is 5-10 times lower than the values needed with conventional waveguides. In terms of a practicality index defined via switching power times waveguide length, this waveguide has around the best value     

All-optical switching technologies for protection applications

One of the key issues when designing an optical transport network is how to ensure survivability in the event of a network failure. With the increased penetration of dynamic DWDM networks the demand for new, reliable, and flexible protection schemes at the optical layer rises. Furthermore, over the last several years, enormous advances have been made in optical component technologies. As a result, all-optical components, such as the optical switch, now offer additional functionalities. This article examines the applicability of new and legacy all-optical switching technologies to serve as building blocks for different protection applications.     

All-optical nonlinear switching in GaAs-AlGaAs microring resonators

In this paper, we demonstrate all-optical nonlinear switching in compact GaAs-AlGaAs microring resonators at the 1.55-μm wavelength. Switching is accomplished in the pump-and-probe configuration in which the pump-and-probe signals are tuned to different resonance wavelengths of the microring. Refractive index change in the microring due to free carriers generated by two photon absorption is used to switch the probe beam in and out of resonance. Measured transient responses of the pump and probe through the microring show good agreement with theoretical predictions based on nonlinear pump-probe interaction due to two photon absorption     

All-optical bistable switching in nonlinear directional couplerloaded with Bragg reflector

A GaInAsP nonlinear directional coupler loaded with a Bragg reflector has been fabricated. All-optical bistable switching in the fabricated device is demonstrated at a wavelength of 1.55 μm     

All-optical switching in an angled-grating semiconductor Braggamplifier

We propose an all-optical switching element based on forward Bragg diffraction in a periodically corrugated semiconductor laser amplifier. The device geometry is similar to that of an angled-grating distributed-feedback (α-DFB) laser except that there is no reflective feedback. Light induced changes in the refractive index cause the output to switch from a cross state to a bar state with input power levels of only a few milliwatts     

All-optical switching in phase-shifted fiber Bragg grating

A low-power all-optical-switching in a phase-shifted grating has been experimentally demonstrated at 1.55 μm. The grating is written in a standard fiber for communication and the switching is based on the cross-phase modulation induced by an intense pump pulse on a low intensity probe. An extinction ratio of more than 6 dB has been achieved for 1 kW pulse peak power. The strong enhancement of the nonlinear effect due to the group velocity reduction and the switching polarization dependence have been theoretically investigated and experimentally confirmed     

All-optical switching based on self-assembled halide perovskite microwires

Optical switching is a fundamental element in all-optical integrated circuits and networks with ultrahigh speed and low energy consumption compared to their electronic counterparts.Switching on/off the waveguiding with another light beam demands large optical nonlinearity to compactify device footprint and decrease energy consumption,which is difficult to achieve in photonic systems.     

Random switching techniques for inverter control

New techniques which dramatically reduce acoustic noise by randomising the inverter switching frequency for inverter control are presented. It is shown that the proposed techniques combine the advantages of conventional pulsewidth modulation (PWM) techniques based on regular-sampling techniques and random PWM techniques     

All-optical bistable switching in an active InGaAs quantum-well waveguide

The authors have observed low-power optical bistability in an active strained InGaAs single-quantum-well waveguide which is biased with a quasi-constant current injection 20% below the threshold current. Although the output power measured after the output collecting lens is half of the peak input power measured before the input focusing lens, it is believed that this is mainly due to the inefficient coupling into a slab mode, and that optical switching occurs with net gain in the device. A channel waveguide with a similar active medium would operate with constant DC electrical bias and should provide significant overall gain.<>     

All-optical switching in prism coupling to semiconductor-doped glass waveguides

Optical switching was observed within a pulse train during prism coupling into a nonlinear potassium-ion-exchanged semiconductor-doped-glass waveguide with modified composition. An interpretation of the observed phenomenon is given in terms of a slow (probably thermal) nonlinearity.     

All-optical switching by counterpropagating operation in cascadedsemiconductor optical amplifiers

We propose a simple, compact, integrative, flexible, power-efficient, and all-optical switch. The operation is based on self-induced gain modulation leading to nonlinear transmittance with a threshold level dependent on input powers of the data and control signals counterpropagating in cascaded semiconductor optical amplifiers. We demonstrate numerically the all-optical switch with small-signal modulation, low-power consumption, high-output power, and high-output extinction ratio     

All-optical switching of infrared optical radiation using isotropicliquid crystal

Experimental results of the transmission to total-internal reflection switching of a step-on CO₂ laser beam by a dielectric-clad, isotropic liquid crystal film is presented. The use of the isotropic phase allows for polarization independence of the processes, while maintaining a moderate thermal nonlinearity. Dependence of switching speed on incident angle and energy density is evaluated. Experimental observations of the nonlinear switching effect with microsecond CO₂ laser pulses are also presented     

All-optical pulse switching in twin-core fiber couplers withintermodal dispersion

Due to the dispersion mismatch between the two supermodes of a two-channel coupler, pulse switching cannot be analyzed without taking into account the effect of intermodal dispersion. Using full numerical simulations, we show the influence of intermodal dispersion on all-optical switching with ultrashort pulses in twin-core fiber couplers. For the nonlinear regime, however, only subpicosecond and femtosecond pulses are affected in the cross state since the parallel state remains almost unaffected     

Zero-voltage switching for three-level capacitor clamping inverter

A zero-voltage switching (ZVS) scheme for a three-level capacitor clamping inverter based on the true pulsewidth modulation (PWM) pole is proposed in this paper. With this scheme, the main switches work with ZVS through the assistance of a small rating zero current switching (ZCS) lossless auxiliary circuitry without imposing any voltage/current spikes on the main devices or any extra control complexities. Consequently, a three-level capacitor clamping inverter system can operate at a promoted switching frequency and becomes more eligible to be considered for high-power advanced applications, for example, in high-speed drives or power active filter areas. In this paper, the main circuit operation issues as regards the clamping voltage stability, damping capacitor stress, and output voltage spectrum are shortly reviewed first, after which the commutation principle, auxiliary circuitry stress analysis, and auxiliary circuitry designing methodology are presented in detail. Experimental results from a 700 V supply 3 kW half-bridge three-level capacitor clamping inverter are demonstrated which conform well to the proposal     

Program-controlled soft switching PRDCL inverter with new space vector PWM algorithm

A soft switched space vector PWM inverter is developed using new parallel resonant DC-link (PRDCL). This PRDCL can operate on variable DC-link pulse position and width resulting in enhanced PWM capability, which is superior to other resonant DC-links. A new space vector algorithm is presented suitable for this PRDCL inverter. The suggested algorithm is able to eliminate narrow PWM pulses that impede DC-link operation. This PWM control, however, requires complex and precise timing sequences in relation to PRDCL operation, which is nicely solved by adopting a new programmed controller with a buffer and a programmable timer.     

All-optical switching in 3,3'-diethyl-2,2'-thiatricarbocy-anine Iodide dye molecules

All-optical switching has been theoretically analyzed in the 3,3'-diethyl-2,2'-thiatricarbocyanine iodide(DTTCI) carbocyanine dye that exhibits large excited-state absorption to achieve high contrast and fast switching.Switching has been analyzed both ns and ps pump pulse widths.It is shown that there is an optimum value of concentration for given peak pump intensity at which maximum modulation can be achieved.We can get 93.84% modulation of transmission of a CW probe laser beam at 532 nm at peak pumping in...     

All-optical switching using color centers in an irradiated phosphorus-doped fiber

We report on all-optical switching of a 900-nm signal in a two-mode silica fiber based upon a resonant nonlinearity introduced by phosphorus color centers in a 22-cm irradiated P/sub 2/O/sub 5/-SiO/sub 2/ fiber. Full switching was observed with only 1 /spl mu/J of absorbed 532-nm pump energy, with a projected response time under 10 ns. This switch required a peak power two orders of magnitude lower than for a fiber Kerr effect device operated under identical conditions.     

All-optical remote switching for multiplexed optical fiber sensorsand communications systems

All-optical self-routing switches are described which automatically route optical data signals. These switches require no separate source of power, and have been demonstrated to operate from a single input laser beam of 300 μW. The input laser beam contains the data, destination address, and optical power. These optical switches can be used for all-optical communication systems, and are used as an example in this paper to demonstrate remote switching via an optical fiber to a sensor. The sensor modulates the optical carrier which returns the modulated carrier to the source end of the fiber. The switch demonstrates auto-aligning properties which ensure correct rerouting of the modulated signal back to the source. Operation has been demonstrated for all the visible lines of an argon ion laser     

All-optical Gbit/s switching using nonlinear optical loop mirror

The switching of a 20 Gbit/s pulse train at 2.5 Gbit/s in an all-fibre NOLM is demonstrated. An entirely semiconductor case powered configuration was used with a long loop (6.4 km) ensuring low power (10 mW) for the switching pulses.<>