Fabry-Perot Semiconductor Optical Amplifier Research Articles

Optical hysteresis shape transformation using linear polarization components

We provide a mathematical model to elucidate how a linear polarizer can be used to transform the shape of an optical-power hysteresis curve into the canonical counterclockwise (CCW) shape, clockwise (CW) shape, and upward-switching and downward-switching butterfly shapes. This transformation is possible for optical signals whose states of polarization also exhibit hysteresis. Critical to our model is a generalized Malus' law that accounts for elliptical input polarization as well as insertion loss, finite extinction ratio, and pass-axis orientation angle of the linear polarizer. The generalized Malus' law reveals that the transmittivity of the polarizer itself exhibits a bistable hysteresis curve, and this transmittivity acts on the input-power hysteresis curve to produce the variety of output-power shapes. Additionally, we model the optimization of the hysteresis contrast of the CCW and CW shapes, achieving 20 dB or more by using a polarization controller placed upstream of the polarizer. Modeling and experimental validation are carried out using a polarization-varying bistable signal generated by an anisotropic Fabry–Perot semiconductor optical amplifier, and the results are applicable to other nonlinear resonators and means of polarization-varying signal generation. This model can be used for the study, design, and optimization of a variety of sequential and combinational all-optical signal processing applications.

Simultaneous nonlinear polarization rotation and dispersive optical bistability: theoretical and experimental analysis

We study the simultaneous occurrence of dispersive optical bistability and nonlinear polarization rotation in a nonlinear photonic resonator. The demonstrated bistable hysteresis curves of the Stokes parameters broaden the notion of optical bistability in nonlinear resonators beyond that of the traditional optical-power hysteresis curve. We present a theoretical model to fully understand the polarization hysteresis curves observed in the laboratory and to establish the relevant scaling parameters for bistable action. By optimizing the optical-signal power injected into each polarization mode of the resonator and optimizing the small-signal birefringence of the resonator by selection of the signal wavelength, a polarization rotation of 30% orthogonality was achieved between stable polarization states in the lab. The theoretical and experimental methods reported here are carried out for the case of a Fabry–Perot semiconductor optical amplifier, and are extendable to the investigation of simultaneous occurrence of these phenomena in other nonlinear media (such as Kerr media) and other photonic resonators.

An analytical study on bistability of Fabry-Perot semiconductor optical amplifiers

Abstract Optical bistabilities have been considered to be useful for sensor applications. As a typical nonlinear device, Fabry-Perot semiconductor optical amplifiers (FPSOAs) exhibit bistability under certain conditions. In this paper, the bistable characteristics in FPSOAs are investigated theoretically. Based on Adams’s relationship between the incident optical intensity I in and the z-independent average intracavity intensity I av, an analytical expression of the bistable loop width in SOAs is derived. Numerical simulations confirm the accuracy of the analytical result.

Cross‐polarisation modulation‐based ultrahigh contrast operation of a Fabry–Pérot all‐optical AND gate

A 31.2 dB-contrast optical AND gate based on a Fabry–Perot semiconductor optical amplifier is experimentally demonstrated, exceeding previously demonstrated data for such a device by over 24 dB. Whereas cross-phase modulation shifts the Fabry–Perot resonance to trigger the AND-gate functionality, cross-polarisation modulation enables ultrahigh contrast by producing a state of polarisation (SOP) for the high output-power state that is different than that of the low output-power state; a linear polariser is then used to block the low-power SOP. This technique is applicable to other resonator geometries, Kerr-nonlinear media, and to other all-optical combinational-logic gates.

All‐optical flip‐flop contrast enhancement based on bistable polarisation rotation within Fabry–Perót SOA

Switching-contrast enhancement of over 28 dB for all-optical flip-flop (AOFF) operation of a Fabry–Perot semiconductor optical amplifier (SOA) is experimentally demonstrated. Although the two stable flip-flop states of such a device are typically distinguished by their optical power, it is demonstrated that each stable state can also exhibit a unique state of polarisation (SOP). This bistable polarisation rotation (BPR) is leveraged to achieve extreme contrast enhancement by aligning the AOFF reset-state SOP to the blocking axis of a linear polariser, producing a contrast of 36.6 dB. This contrast-enhancement technique is applicable to other AOFFs based on resonant-type SOAs (RT-SOAs) and Kerr-nonlinear media, substantially improving their applicability to advanced photonic-switching applications.

All-Optical Clock Recovery Using a Single Fabry–Perot Semiconductor Optical Amplifier

We present and demonstrate all-optical clock recovery (CR) from the input single- and multiwavelength return-to-zero (RZ) data, using a single multiquantum-well Fabry-Perot semiconductor optical amplifier (FP-SOA) with no additional amplitude equalization measures. The influence of the FP-SOA facet reflectivity on the amplitude equalization of the recovered clock was numerically investigated. A stable 36.55 GHz optical clock with an extinction ratio of 11.0 dB and a root-mean-square timing jitter of 575 fs was extracted from the input, which consisted of pseudorandom binary sequences of RZ data. The presented scheme has the potential to perform CR from more than 100 Gbit/s of RZ data, and it has the advantage of wideband and parallel operation.

Single Passband Microwave Photonic Filter With Continuous Wideband Tunability Based on Electro-Optic Phase Modulator and Fabry–Pérot Semiconductor Optical Amplifier

We propose and experimentally demonstrate a microwave photonic filter based on an electro-optic phase modulator (EOPM) and a Fabry-Perot semiconductor optical amplifier (FP-SOA). A microwave photonic filter with a single passband between 0 and 40 GHz is obtained. In the single passband microwave photonic filter, the microwave subtraction effect is introduced in optical domain to improve the performance. A theoretical model is established to describe the operation principle of the microwave photonic filter, and the predicted results show good agreement with the experimental results. In the experiment, the center frequency and the 3-dB bandwidth are 18.3 GHz and 99.5 MHz, respectively, with the corresponding Q factor of 184, and the rejection ratio and shape factor are 34.3 dB and 5, respectively. The continuous wideband tunability of the microwave photonic filter is also demonstrated by adjusting the bias current of FP-SOA.

Tunable 19 × 10 GHz L-band FP-SOA based multi-wavelength mode-locked fiber laser

We present a multi-wavelength mode-locked fiber ring laser incorporating a semiconductor optical amplifier (SOA) and a Fabry–Perot semiconductor optical amplifier (FP-SOA). Because the gain of the SOA is depleted by an external injection optical signal, the SOA acts as a loss modulator. The FP-SOA serves as a tunable comb filter. The presented laser source can generate 19 synchronized wavelength channels with the extinction ratio of about 21 dB, each mode-locked at 10 GHz, and mode-locked pulse width is about 40 ps. Oscillation wavelengths band can be tuned by adjusting the bias current of the SOA, and wavelength spacing also can be changed by using a tunable optical delay line (ODL) or a temperature controller. The polarization-insensitive devices ensure that the output power is rather stable. This fiber laser has potential applications in longer waveband (L-band) within the low-attenuation window.

Single and Multiwavelength All-Optical Clock Recovery Using Fabry–PÉrot Semiconductor Optical Amplifier

We experimentally demonstrate an all-optical clock recovery scheme for the return-to-zero data with single- and multiwavelength. This scheme is mainly based on clock-like pulse generation from an active filter with a multiquantum-well Fabry-Perot semiconductor optical amplifier and amplitude-equalization with self-nonlinear polarization switching. We obtain stable and low jitter optical clock signals in single and dual channels using this scheme, which has some distinct advantages including easy integration, free preamplification, convenient tuning, good tolerance to long ldquo0srdquo data, and greater tolerance to the stability of the input wavelength.

Time-to-live decrementing scheme in optical packet switching

Feature Issue on Photonics in SwitchingA novel scheme of decrementing one time-to-live pulse based on an asymmetric Mach-Zehnder interferometer and a Fabry-Perot semiconductor optical amplifier is proposed. The asymmetric Mach-Zehnder interferometer transfers M time-to-live pulses into M−1 pulses and two residual pulses with a 6 dB power difference. The Fabry-Perot semiconductor optical amplifier, where the gain fluctuates with the change of the carrier density and the gain increases with the depletion of the carrier in a certain region, amplifies the M−1 pulses and suppresses the two residual pulses. A numerical model is established for verifying the feasibility of this scheme. The effects of injecting current, pulse power, period, and width are discussed.

Rate Equations for modeling dispersive nonlinearity in Fabry-Perot semiconductor optical amplifiers

We model the non-linear gain characteristics of a Fabry-Perot semiconductor optical amplifier using a modified photon density rate equation. Good agreement is found with experimental results, with the simulation accurately reproducing all the major characteristics of the amplifier. To our knowledge, this is the first calculation using only the rate equations that accurately predicts the gain and nonlinear behavior of FPSOAs.

Noninverted wavelength conversion using Fabry–Perot semiconductor optical amplifiers

Noninverted wavelength conversion has been demonstrated using Fabry–Perot semiconductor optical amplifiers (FP-SOAs), and its mechanism is theoretically analyzed. The noninverted behavior is dominated by the shift of gain spectrum in the FP-SOA. Increasing the input optical power suppresses the spontaneous emission and drives the gain spectrum toward the longer wavelength side due to the enhancement of carrier–photon interaction. The performance of wavelength converters is improved owing to the resonant effect at the probe wavelength and this type of converter provides an effective approach for wavelength conversion in the future broadband networks.

Optical gain and refractive index of a laser amplifier in the presence of pump light for cross-gain and cross-phase modulation

The wavelength dependent changes in optical gain and refractive index in a Fabry-Perot semiconductor optical amplifier are measured for various detunings of the pump wavelength from the quasi-Fermi level separation. The refractive index change is nearly constant over a very large wavelength range. We also present data for the linewidth enhancement factor due to optical injection. Estimates of the carrier densities and stimulated recombination rates are made using our optical gain model based on realistic band structure calculations for a strained quantum-well laser. Our results are very useful for ultra-broad-band wavelength conversion by cross-gain and cross-phase modulation (XGM, XPM).

Measurements of the gain spectrum of near-travelling-wave and Fabry-Perot semiconductor optical amplifiers at 1.5 µm

We discuss the relationship between facet reflectivity and gain bandwidth in semiconductor optical amplifiers and present the first high-resolution measurements of the gain spectrum of InGaAsP 1 · 5 µ optical amplifiers. The relatively smooth gain spectrum and high output power of near-travelling-wave amplifiers are compared with those of Fabry-Perot amplifiers.