Effects In Semiconductor Optical Amplifier Research Articles

Enhanced ultra-wideband optical frequency comb generation based on cross-polarization modulation effect of semiconductor optical amplifier

Enhanced ultra-wideband optical frequency comb generation based on cross-polarization modulation effect of semiconductor optical amplifier

Theoretical study on fast and slow light effects in semiconductor optical amplifiers under assist light injection

In this paper, the fast and slow light effect of semiconductor optical amplifiers (SOAs) under assist light injection is theoretically analyzed. Coherent population oscillation (CPO) is used to induce fast and slow light effect in the theoretical model. The effects of parameters such as modulation frequency, modulation current and assist optical power on phase delay are investigated under the assist light injection. These effects are then compared with the case without assist light injection. The simulation results show that the injection of assist light can increase the phase delay of the output optical signal and enhance the slow light effect. Furthermore, when the assist light optical power is in the range of 0–15 dBm, the slow light effect is strong.

Numerical analysis of slow and fast light effect in semiconductor optical amplifier with certain facet reflection

In this paper, the slow and fast light (SFL) effects of the semiconductor optical amplifier (SOA) having certain facet reflections are theoretically investigated. The theoretical model is used to account for the SFL phenomenon causing the coherent population oscillation. The influence of the current modulation frequency, the value of the current, the linewidth enhancement factor, facet reflectivity as well as the relative phase of the modulated current on the phase delay in the SOA are studied. It is demonstrated that the SFL effect could be controlled by the modulation frequency, the value and relative phase of the current. Finally, it is shown that the magnitude of the SFL delay could be tuned by a change in the linewidth enhancement factor as well as the facet reflectivity of the SOA.

All optical multi‐functional signal processing scheme for D8PSK and DQPSK format using four‐wave mixing in semiconductor optical amplifiers

AbstractIn this article, a multifunctional optical processing unit for differential eight phase‐shift‐keying (D8PSK) and differential quadrature phase‐shift‐keying (DQPSK) based on four‐wave mixing (FWM) effects in semiconductor optical amplifier (SOA) is proposed. All‐optical wavelength conversion, D8PSK‐to‐DQPSK format conversion and signal encryption of 10‐Gbaud DQPSK and D8PSK optical signals are achieved simultaneously by simulation. Detailed theoretical analysis and simulation results are conducted to verify the feasibility of the scheme. The Q factor of the electrical signals and the bit error rate recovered from wavelength and format converted components are approximated to be around 6, and 10−9, which indicates the feasibility of the scheme. For the encrypted signal, the FWM effect of another SOA is utilized to decrypt the encrypted signal, and the encryption function of 10‐Gbaud DQPSK and D8PSK optical signals is also verified.

Optical chaotic communication using correlation demodulation between two synchronized chaos lasers

This paper theoretically investigates the scheme of optical chaotic communication based on correlation demodulation between two synchronized semiconductor lasers. In the scheme, a semiconductor laser (SL) system, which is subject to phase conjugation and electro-optical phase modulation feedback, generates optical chaos with high-complexity, simultaneously, the time-delay (TD) signature can be well concealed. We use the digital signal “0” and “1” to control the chaotic signal’s switching between two arms of electro-optical (E-O) switch to indirectly achieve spreading spectrum. Concretely, for the “0” bit, at the cross arm the waveform of the optical chaotic signal is reversed by utilizing the cross gain modulation (XGM) effect of semiconductor optical amplifier (SOA); for the “1” bit, the chaotic signal is exchanged from the cross arm into the through arm. Based on the four-wave mixing (FWM) effect of optical parameter amplifier (OPA), the optical chaotic signal is converted to the same center wavelength as SOA’s output, and then two chaotic sequences are coupled into a channel in turn, as a results, the power of the signal of 5 Gbit/s is uniformly distributed and expanded to about 23.45 GHz bandwidth, thus its power spectrum density (PSD) becomes very low. We numerically demonstrate that this chaotic dynamics between the transmitter and the receiver can be identically synchronized due to coupling. The results indicate that the novel correlation-demodulation-based optical chaotic communication scheme can tolerate a higher noise level, and it can achieve a high-quality communication under lower signal-to-noise ratio (SNR). Compared with the scheme of synchronized error monitor, the correlation demodulation way has better ability for anti-noise interference.

Influence of co- and counter-propagating light on the phase-mismatch effect in semiconductor optical amplifiers

The phase-mismatch effect, caused by the difference in confinement factor between transverse electric (TE) and transverse magnetic (TM) modes, has not been observed in semiconductor optical amplifiers (SOAs) and is not typically accounted for. In this work, we investigate the characteristics of the phase-mismatch four wave mixing (FWM) effect, which occurs in SOA devices. Our results reveal a sinc-like response in the intensity of co- and counter-FWM conjugates as a function of the detuning shift between interacting beams. It is demonstrated that the coherence lengths between the phase match/mismatch cycles differ between co- and counter-propagating nondegenerate FWM experiments and depend on the amplified TE/TM polarizations of interacting waves aligned with respect to the birefringent axes of SOAs. The coherence lengths between each phase match/mismatch cycle in co-propagation experiments are found to be 1600 and infinite GHz, respectively, compared to 800 and 400 GHz found in counter-propagation experiments.

Phase-mismatch dependence of the four-wave mixing effect in semiconductor optical amplifiers.

The phase-mismatch effect due to polarization-dependent mode confinement factor has been shown to be not a crucial problem in semiconductor optical amplifiers (SOAs) and is usually not accounted for. The phase-mismatch four-wave mixing (FWM) process in SOA devices is experimentally reported. The results reveal a sinc-like behavior in the intensity of FWM conjugate as a function of wavelength separation between transverse electric (TE)/transverse magnetic (TM) pumps due to induced confinement factors difference. Efficient FWM occurred for a detuning shift of about 500 GHz, limited by phase-mismatch conditions and determined by coherence length required for low and high frequencies to complete a full phase-match cycle. Phase-match FWM with an infinity coherence length can be fulfilled by proper alignments of co-polarized TE/TM modes of input waves with respect to the birefringent axes of the device structure.

All-optical logic gate NAND using semiconductor optical amplifiers with simulation

Hybrid encoding technique for the representation of the binary states of information, four-wave mixing in semiconductor optical amplifier (SOA) as frequency generator and cross-polarization rotation effect in semiconductor optical amplifier as a frequency converter are used to design all-optical universal logic gate NAND. The devices can perform ultrafast operation and easily integrable. The simulated results of the proposed logic gate ensure feasibility of the proposals.

All-Optical Modulation Format Conversion Between OOK, QPSK, and 8QAM

Modulation format conversion is useful when the signal is transmitted through networks employing different modulation formats. It is also expected to increase the spectral efficiency and reduce power consumption in network nodes by applying all-optical signal processing to the modulation format conversion. In this paper, we propose an all-optical modulation format conversion system between on - off keying, quadrature phase-shift keying, and 8-ary quadrature amplitude modulation using optical nonlinear effects in semiconductor optical amplifier and optical threshold device. We also evaluate the conversion performances of the system by numerical simulation in terms of optical signal-to-noise ratio, optical signal power, and accumulated chromatic dispersion.

Spectral signature of nonlinear effects in semiconductor optical amplifiers.

Optical spectra of signals at the output of semiconductor optical amplifiers (SOA) provide useful insight into amplifier nonlinearities. In this work, we determine the parameters of an analytical SOA model with a pump-probe experiment by evaluating the measured spectra of the pump and probe pulses at the SOA output. The analytical lumped SOA model considers carrier depletion, carrier recovery, spectral hole burning, two-photon absorption, and we include an additional effect termed 'two-photon induced free-carrier absorption', that is responsible for creating an identifiable blue-shifted component in the spectra. We are able to relate the underlying physical nonlinear effects to the spectral peculiarities of the output pump and probe spectra, and give guidelines for the exploitation of these nonlinear effects for optical signal processing. In addition, with a much-simplified SOA model and by replacing the pump pulse with modulated data we show that the output spectrum is altered in a manner consistent with phase patterning effects.

Photonic processing of all‐optical Johnson counter using semiconductor optical amplifiers

This study presents a novel design of Johnson counter using D flip-flops. The performance of D flip-flop is carried out by exploiting the cross-gain modulation effect in semiconductor optical amplifier (SOA), purging the use of components like polarisation controllers, switches and so on. Performance is evaluated in terms of various variants like operational speed, cost effectiveness of design, rise time/fall time, quality of signal received and the system is found to give better results in terms of extinction ratio even without any feedback path. The Johnson counter or twisted ring counter is implemented using three all-optical D flip-flops producing six states. The D flip-flop incorporates travelling wave SOA and all-optical NOT gate. The proposed counter is reasonably valuable as it desires half of the flip-flops in association to other ring counters which directly reduce the cost of the system.

A Novel Security Enhanced Decoder Based on XOR Detection for Optical Code Division Multiple Access System Using Multi-Diagonal Code

Objective: The main aim of this research paper is to design a security enhanced decoder based on the XOR logic gate detection technique. Methods/Statistical Analysis: An all optical XOR gate has been designed by using Semiconductor Optical Amplifier (SOA) for the secure transmission in Optical code division multiple access system. Multi Diagonal (MD) code is implemented with all optical logical gate detection using non-linear effects in semiconductor optical amplifiers. To realize the XOR gate, two identical SOAs in MZI structure have been used. Finding: The Non-Return-to-Zero (NRZ) and RZ bit format have been compared and results show that using NRZ bit format the performance is better than RZ bit format and its optimum power comes out to be 0.6mW. A new design of Multi-diagonal code has been proposed by using all optical logical gate detection considering nonlinear effects in SOA. The design has successfully worked at Bit Error Rate (BER) 8.77×10 -09 . Application/Improvements: This design having decoder based on XOR logic gate utilizing the Multi-diagonal code will have wide applications in military for the secure transmission of data.

100-Gb/s 2R regeneration using cross gain compression in semiconductor optical amplifiers.

All-optical 2R regeneration of 100-Gb/s on-off-keying (OOK) signal is experimentally demonstrated based on cross gain compression (XGC) effect in semiconductor optical amplifiers (SOAs). It is shown that a high-quality logic-inverted signal and SOAs with faster gain recovery times are the two key enabling factors for obtaining regeneration results at such speeds. BER improvement of 1.2~2 dB is experimentally obtained at 1551 nm and regenerative results are demonstrated on a wide wavelength range from 1535 nm to 1555 nm. The tolerance of the input signal to optical signal-to-noise ratio (OSNR) deterioration is also experimentally studied for the 2R regeneration scheme at two different wavelengths.

Design of an All Optical 3-Bit Modulo Eight Asynchronous Up Counter

The paper presents an all-optical 3 bit up counter with complete Boolean functionality as a representative circuit for modeling and optimization of monolithically integrated components. Here, the proposed logic unit design is based on nonlinear effects in semiconductor optical amplifiers (SOA).These equations are first solved to generate the pump, probe and conjugate pulses in a SOA. The pulse behavior are analyzed and applied to realize behavior of all-optical NAND gate. Next, the logic is used to implement All-Optical D Flip-Flop logic, and its function is verified with the help of truth table. Finally with the help of three D Flip-Flops, a 3-bit up counter is proposed.

Theoretical analysis of carrier heating effect in semiconductor optical amplifiers

This paper reports an accurate and simple analytical method to study carrier heating effect in semiconductor optical amplifiers using both Fermi–Dirac integrals of 3/2 and 1/2 orders. Global approximations for Fermi–Dirac integrals of 3/2 and 1/2 orders are adopted to obtain the analytical expression for the carrier temperature. The amplification of a single strong pico-second pulse having different peak powers is studied both with and without carrier heating effect. It has been found carrier heating impose more distortion on the amplified pulse, including suppressing the peak power value, increasing the peak temporal shift and broadening the bandwidth of amplified output signals. Also, when the input signal peak power or the pump current increases because of carrier heating effect the carrier temperature increases too. We have studied the amplification of 80 Gbit/s pico-second pulse sequences and found an increase in the peak value of the amplified output signal due to the pronounced fast gain recovery process induced by the carrier heating effect.

Chromatic dispersion monitoring using semiconductor optical amplifier

An all-optical real-time chromatic dispersion (CD) monitoring technique is proposed and demonstrated for 40 Gbit/s differential phase-shifts keying (DPSK) signal, utilizing the cross modulation effects of semiconductor optical amplifier (SOA). The optical power of the output spectral components, which is from the probe’s frequency up to the signal bandwidth, is used for CD monitoring. This technique provides a wide monitoring range with large variation scale. The impacts of the polarization mode dispersion (PMD) and the optical signal-to-noise ratio (OSNR) on the CD monitoring results are theoretically analyzed and then experimentally investigated, showing that they have slight influence on the monitoring results within a certain range. Furthermore, simulated results for quadrature phase shift keying (QPSK) signal at 80 Gbit/s are also demonstrated, indicating that this technique is suitable for advanced modulated format as well.

Dynamic model of slow light in a tensile-strained semiconductor optical amplifier

The slow light effect in semiconductor optical amplifiers has many potential applications in microwave photonics such as phase shifting and filtering. Models are needed to predict the slow light effect in SOAs and its dependence on the bias current, wavelength, and power and modulation index. In this paper we predict the slow light characteristics of a tensile-strained SOA by using a detailed time-domain model. The model includes full band-structure based calculations of the material gain, bimolecular recombination and spontaneous emission, a detailed carrier density rate equation and travelling-wave equations for the amplitude modulated signal and amplified spontaneous emission. The slow light parameters of interest include the beat signal phase shift and amplitude response. The model predictions show good agreement with experimental trends reported in the literature.

All optical SR and D flip-flop employing XGM effect in semiconductor optical amplifiers

This paper presents a simple and novel scheme for all-optical SR and D flip-flop employing cross gain modulation (XGM) effect in two wideband semiconductor optical amplifiers. The proposed flip-flop has a fast response, with less than 20ps transition times for both rising and falling edges. The FF speed-limit is mainly determined by the SOA recovery time and the intra-FF coupling length. The simulation results exhibit a contrast ratio of 13dB between two states with an AM of less than 2.5dB.The distinctive simplicity of the flip-flop implies reduced footprint and low power consumption which makes it ideal for photonic integration.

A special issue on photonic signal processing

Photonic signal processing has been receiving increasing attention for about fifteen years. It would be enabling technology for next generation large capacity optical networks because it can avoid electronics bottleneck and decrease power consumption greatly. There are two main areas related to photonic signal processing. One topic is all-optical signal processing for digital bit sequence in optical network, such as all-optical wavelength conversion, alloptical logic operation, all-optical 3R regeneration, all-optical clock recovery, all-optical buffer, etc. The other topic is microwave photonic signal processing, such as microwave photonic filters, arbitrary waveform generation, RF signal generation, UWB signal generation, etc. However, there are still many problems to be solved before these functions could be used in optical networks. Researchers all over the world are concentrating on realizing photonic signal processing functions with some characteristics such as high operation speed and large bandwidth, flexible and multifunctional, potential integration. This special issue on photonic signal processing of Frontiers of Optoelectronics in China has collected review and research articles by a number of Chinese and international experts, especially from the research group sponsored by the National Basic Research Program of China (Grant No. 2011CB301700). There are seventeen excellent papers in this special issue including 4 review articles and 13 research articles. Prof. Yong Liu is a well known specialist in the field of photonic signal processing, and he reviewed some signal processing functions with nonlinear effects in semiconductor optical amplifiers. A wonderful review paper on slow light with silicon photonic crystals was given by Prof. Eric Cassan from University Paris-Sud, and he discussed the challenges, hot research topics and future trends in this field. Prof. Xinwan Li from Shanghai Jiao Tong University reviewed somemicro/nanostructure photonic devices for photonic signal processing, such as micro/nanofiber based devices and silicon waveguide based devices. Dr. Enming Xu reviewed some results on microwave photonic filters with semiconductor optical amplifiers. Moreover, there are 13 research articles focusing on photonic signal processing. An invited paper on compact silicon and hybrid plasmonic waveguides used for signal processing was presented by Prof. Yikai Su from Shanghai Jiao Tong University. Prof. Xianmin Zhang’s group presented a novel method for compensating dispersion effect in phase modulated radio over fiber links using an optical carrier Brillouin processing technique. Recent progress on slow light with cascaded microring resonators was reported by Prof. Jinzhong Yu’s group. Yu Ji from Prof. Jian Wu’s group demonstrated 40 GHz phase stable optical pulses with pulse-width of 1.88 ps, extinction ratio larger than 20 dB, the timing jitter of 57 fs and signal-to-noise ratio of 32.8 dB. Prof. Caiyun Lou and her colleagues also reported some research progress on optical signal processing functions with semiconductor optical amplifiers and delay interferometers. Some results on all-optical clock recovery with magnetically controllable fiber optical parametric oscillator were demonstrated by Prof. BaojianWu. Ping Zhao from Xinliang Zhang’s group presented a novel method for fabricating silica micro/nanofiber. Also, there are some theoretical simulation results in this special issue. Xinying Li from Prof. Nan Chi’s group analysed the impact of quadrature imbalance in the presence of frequency offset in an optical coherent offset quadrature phase-shift keying receiver. Prof. Guangqiong Xia and her colleagues analysed the impacts

Investigation of the effects of SOA locations in the linear cavity of an O-band Brillouin SOA fiber laser

An investigation into the effect of semiconductor optical amplifier (SOA) location in an O-band Brillouin SOA fiber laser (BSFL) was performed. Better output peak power flatness was generated by placing the SOA after the nonlinear medium, which is a 20 km true wave fiber (TWF) than placing it before the TWF. A maximum power of six flat output peaks with average power of −22.0 dBm for a BP (Brillouin pump) wavelength of 1320 nm was obtained, generated from a BSFL with a SOA located after the TWF, compared with three flat Stokes signals with the SOA before the TWF at a BP wavelength of 1310 nm. The flat peak power output for the O-band Brillouin fiber laser is important, especially in producing a good O-band source.