Cascaded Semiconductor Optical Amplifiers Research Articles

Simultaneous up- and down-frequency mixing based on a cascaded SOA-MZIs link.

In this paper, a simultaneous frequency up- and down-conversion is performed using a cascaded semiconductor optical amplifier Mach-Zehnder interferometers (SOA-MZIs) link for radio-over-fiber (RoF) applications. The intermediate frequency (IF) signal carrying quadratic phase shift keying (QPSK) data at a frequency f1 is up-converted at the SOA-MZI1 output at nfs±f1, where n is the harmonic rank of the first sampling signal. In addition, this up-converted signal is concurrently up- and down-converted at the SOA-MZI2 output at mfs+nfs±f1 and |nfs±f1-mfs|, respectively, where m is the harmonic rank of the second sampling signal. Using the virtual photonics integrated (VPI) simulator, it has been shown that the optical transmission system based on a cascaded SOA-MZIs link has a better efficiency and more endurable quality of the frequency mixing of QPSK signals and the higher frequency range for up- and down-conversions. Positive conversion gains are obtained at the highest mixing frequency of 101.9 and 86.3 GHz for up- and down-conversions, respectively. The best error vector magnitude provided using a cascaded SOA-MZIs link is 15.5% at the mixing frequency of 101.9 GHz for up-conversion and 18% at 86.3 GHz for down-conversion at the bit rate of 40,500 Mbit/s. The maximum bit rates of 40.5, 81, and 121.5 Gbit/s for QPSK, 16-QAM, and 64-QAM modulations, respectively, that meet the forward error correction limit is fulfilled by using a cascaded SOA-MZIs link. Another advantage of using the cascaded SOA-MZIs link is the up- and down-conversion simultaneously achieved at the second stage.

All-optical XOR function accompanied with OOK/PSK format conversion with multicast functionality based on cascaded SOA configuration

We proposed a novel all-optical XOR logic accompanied with OOK/PSK format conversion by using cascaded semiconductor optical amplifier (SOA) configuration. Within each SOA, the cross phase modulation and nonlinear polarization rotation processes are properly controlled by OOK signals. The eye diagrams and obtained spectra witnessed the effectiveness of operation. A multicast function is also explored in the process of XOR function, and error-free operation (BER <10−9) with less than 2.5 dB power penalty is obtained.

All-Optical OOK -to-QPSK Modulation Format Conversion With Wavelength Multicasting Based on Cascaded SOA Configuration

An on–off keying (OOK) to quadrature phase shift keying (QPSK) format conversion scheme has been demonstrated in this paper. Two-channel OOK signals are converted into one-channel QPSK signal, and accompanied with a multicast function. The proposed scheme is based on a cascaded semiconductor optical amplifiers (SOA) configuration where the processes of cross phase modulation (XPM) and nonlinear polarization rotation (NPR) are properly controlled by OOK signals in each SOA. The experimental results show that after conversion, four-channel QPSK signals are successfully obtained with open eye-diagrams, and all the converted signals experience a small power penalty of less than 3.4 dB at a bit error rate (BER) of $10^{-9}$ compared to the original signal. In addition, the optical spectra and the constellation diagrams of the converted signal also indicate the high quality performance exhibited by the proposed format conversion scheme.

All-Optical Wavelength Conversion in an InP Photonic Integrated Turbo-Switch

We experimentally demonstrate all-optical wavelength conversion of 56 Gb/s non-return-to-zero (NRZ) signals in an Indium Phosphide (InP) photonic integrated circuit implementing a turbo-switch. The circuit consists of two cascaded semiconductor optical amplifiers (SOAs) with a bandpass filter in between. In this configuration, cross gain modulation (XGM) between a modulated input signal and a continuous wave (CW) light in the first SOA allows to generate a wavelength converted copy of the input signal, while the second SOA, fed by the probe signal selected by the filter, ensures a fast gain recovery. Operations in down- and up-conversion are shown by ER and BER measurements, demonstrating the effectiveness of the photonic integrated circuit (PIC).

10-GB/S bidirectional WDM-PON transmission using spectrum-sliced ASE light sources

We report on a new WDM-PON architecture with the capacity of 10 Gb/s data rate per channel, bidirectional, using low-cost spectrum-sliced incoherent light sources. The system allows the uplink and downlink transmission of a total of 32 channels over 25 km of optical fiber. The experimental results demonstrate bit error rates (BER) below 1.2 × 10−3 for both up- and down-link transmission. With the BER performance, error-free transmission characteristics can be achieved with forward error correction. Several advanced schemes are adopted to realize the high-capacity optical access network. A large effective area fiber is used to reduce the effects of chromatic dispersion for the spectrum-sliced signals. A two-stage cascaded semiconductor optical amplifier configuration is used to suppress the excess intensity noise caused by the incoherent amplified spontaneous emission light source. Remote pumping architecture is applied to compensate for the optical loss. Pretilt process and gain-flattened grating are used to generate uniform channel power with about 3 dB spectrum flatness for uplink and downlink bands.

Principle and applications of semiconductor optical amplifiers-based turbo-switches

All-optical high-speed turbo-switches can effectively increase the switching speed using cascaded semiconductor optical amplifiers (SOAs). The overall recovery time or the bandwidth of turbo-switch was numerically analyzed with time-domain and frequency-domain SOA models. The turbo-switch was explored from the fundamental carrier dynamics in SOAs for the purpose of further increasing its operation speed. An integrated turbo-switch was also been proposed and demonstrated, where a phase adjustable Mach-Zehnder interferometer (MZI) was applied as an optical band-pass filter between SOAs. Wavelength conversion was first demonstrated at 84.8 Gbit/s using the integrated turbo-switch.

基于非线性偏振旋转效应的半导体光放大器级联式高速全光开关

基于非线性偏振旋转效应的半导体光放大器级联式高速全光开关

Two cascaded SOAs used as intensity modulators for adaptively modulated optical OFDM signals in optical access networks.

Detailed theoretical and numerical investigations of the transmission performance of adaptively modulated optical orthogonal frequency division multiplexed (AMOOFDM) signals are undertaken, for the first time, in optical amplification and chromatic dispersion (CD) compensation free single mode fiber (SMF) intensity-modulated and direct-detection (IMDD) systems using two cascaded semiconductor optical amplifiers in a counterpropagating configuration as an intensity modulator (TC-SOA-CC-IM). A theoretical model describing the characteristics of this configuration is developed. Extensive performance comparisons are also made between the TC-SOA-CC and the single SOA intensity modulators. It is shown that, the TC-SOA-CC reaches its strongly saturated region using a lower input optical power much faster than the single SOA resulting in significantly reduced effective carrier lifetime and thus wide TC-SOA-CC bandwidths. It is shown that at low input optical power, we can increase the signal line rate almost 115% which will be more than twice the transmission performance offered by single SOA. In addition, the TC-SOA-CC-IM is capable of supporting signal line rates higher than corresponding to the SOA-IM by using 10dB lower input optical powers. For long transmission distance, the TC-SOA-CC-IM has much stronger CD compensation capability compared to the SOA-IM. In addition the use of TC-SOA-CC-IM is more effective regarding the capability to benefit from the CD compensation for shorter distances starting at 60km SMF, whilst for the SOA-IM starting at 90km.

Suppression of Rayleigh backscattering noise using cascaded-SOA and microwave photonic filter for 10 Gb/s loop-back WDM-PON.

In this paper, we present a novel Rayleigh backscattering (RB) noise mitigation scheme based on central carrier suppression for 10 Gb/s loop-back wavelength division multiplexing passive optical network (WDM-PON). Microwave modulated multi-subcarrier optical signal is used as downstream seeding light, while cascaded semiconductor optical amplifier (SOA) are used in the optical network unit (ONU) for suppressing the central carrier of the multi-subcarrier upstream signal. With central carrier suppression, interference generated by carrier RB noise at low frequency region is eliminated successfully. Transmission performance over 45 km single mode fiber (SMF) is studied experimentally, and the optical-signal-to-Rayleigh-noise-ratio (OSRNR) can be reduced to 15 dB with central carrier suppression ratio (CCSR) of 21 dB. Receiver sensitivity is further improved by 6 dB with the use of microwave photonic filter (MPF) for suppressing residual upstream microwave signal and residual carrier RB at high frequency region.

Gigahertz to terahertz tunable all-optical single-side-band microwave generation via semiconductor optical amplifier gain engineering

We propose and demonstrate a technique to generate low-noise broadly tunable single-side-band microwaves using cascaded semiconductor optical amplifiers (SOAs) using no RF bias. The proposed technique uses no RF components and is based on polarization-state controlled gain-induced four-wave mixing in SOAs. Microwave generation from 40 to 875 GHz with a line-width ~22 KHz is experimentally demonstrated.

All-optical amplitude regeneration of non-return-to-zero differential-phase-shift-keying signal

We propose and experimentally demonstrate amplitude regeneration for non-return-to-zero differential-phase-shift-keying (NRZ-DPSK) signal at 40Gb/s with two cascaded semiconductor optical amplifiers (SOAs) and a subsequent delay interferometer (DI). The amplitude regeneration can reduce the accumulation of nonlinear phase noise (NPN), which is one of the most severe impairments resulting from the intensity fluctuations of the signal in the long haul transmission. The regeneration course includes three stages, which are the NRZ-DPSK to return-to-zero DPSK (RZ-DPSK) format conversion achieved by the cross phase modulation (XPM) effect in a SOA, the amplitude regeneration of RZ-DPSK realized by using the gain saturation effect in a second SOA and the format conversion from RZ-DPSK back to NRZ-DPSK based on a constructive interferometer with a DI. The regenerative performance of the system is characterized in terms of bit-error rate against received power. A power penalty improvement up to 1.2dB is obtained in our experiment.

Theoretical Analysis of High-Speed All-Optical Turbo-Switches

A detailed theoretical model is proposed to simulate the turbo-switch incorporating two cascaded semiconductor optical amplifiers (SOAs). The model takes into account various important physical effects including interband and intraband carrier transitions along with gain dispersion, and bidirectional amplified spontaneous emission. The simulation results are in excellent agreement with the reported experimental measurements. Moreover, simulations of turbo-switch are extended to explain the 160 Gb/s wavelength conversion, pattern effect mitigation, and switch structure optimization. Novel turbo-switch schemes are suggested to further improve the switching speed.

1G / 10G coexistence long-reach PON system using ALC burst-mode SOAs

This paper evaluates the allowable loss ranges of 1G / 10G dual-rate symmetric long-reach 10 gigabit Ethernet passive optical networks (10G-EPONs) that employ cascaded semiconductor optical amplifiers with fast automatic level controlled circuit (ALC-SOAs) for upstream transmission and a single SOA for downstream transmission. Experiments show that our optical amplifiers have the ability to achieve the maximum loss budget of 61dB with very wide loss ranges for both access and trunk spans; they support up to 80km transmission (60km trunk span and 20km access span).

Spectrum reshaping of amplified pulse in silicon nanowaveguide

A device consisting of a cascaded semiconductor optical amplifier (SOA) and silicon on insulator (SOI) optical waveguide is presented to amplify and reshape the frequency spectrum of optical pulses in the picoseconds time duration. Numerical simulations show that the output spectrum of the amplified pulse by SOA can be effectively reshaped by utilizing the SOI waveguide. The length of the SOI waveguide may be judiciously adjusted to significantly reduce the frequency chirp of the output pulse from the SOA resulting in reshaping of the output spectrum. We find that the property of pulse spectrum is sensitive to the input pulse power and its temporal width.

All-optical programmable Boolean logic unit using semiconductor optical amplifiers on the Mach–Zehnder interferometer arms switch

All-optical logic device is a vital element in ultra high speed all-optical networks. If the element is programmable then the device become more sophisticated and user friendly. In this study, a compact all-optical programmable Boolean logic unit (PBLU) is proposed using two cascaded semiconductor optical amplifiers on the Mach–Zehnder interferometer arms-based switches. PBLU can perform any of the 16-Boolean all-optical logical operations (False, AB, AB̄, A, ĀB, B, A⊕B, A+B, ĀB̄, AȯB, B̄, A+B̄, Ā, Ā+B, Ā+B̄, True) according to the programming input. The performance of the circuit is evaluated through numerical simulation, which confirms its feasibility in terms of the choice of the critical parameters.

PATTERN EFFECT MITIGATION IN HIGH-SPEED ALL-OPTICAL SWITCH BASED ON CROSS-GAIN MODULATION IN TWO SOAs WITH DIFFERENT BANDGAPS

Two cascaded semiconductor optical amplifiers (SOAs) with different bandgaps are proposed as an all-optical switch based on cross-gain modulation (XGM) to reduce the pattern effect inflicted by a carrier-lifetime-related long-lived gain recovery tail. We numerically investigate the device gain recovery dynamics in such setup excited by 100 Gbit/s pseudorandom return-to-zero control signal at 1520 nm for different probe wavelengths. The preliminary simulation results indicate that the pattern effect in a SOA in which control pulses are localized in gain region can be reduced by a concatenated SOA in which control pulses are situated in the absorption region. This compensation principle is always valid when the bit rate is beyond 100 Gbit/s.

Optical Packet Replicator Using Cascaded SOA-Based Active Fiber Ring

The optical packet replicator using a cascaded semiconductor optical amplifier (SOA)-based active fiber ring is proposed. By introducing the noncircular assistant light into each stage and adopting a two-stage cascaded structure, 100 replications with identity amplitude are realized. Due to accumulation of amplified spontaneous emission noise, the output signal-to-noise ratio (SNR) of the 100th replication degrades 3.8 dB, which is equivalent to the SNR degradation of 19th replication in a single ring. The number of replications can be controlled by configuring driving pulses of SOA and each interval of hundreds of replications is equal accurately. It can be employed in ultraspeed sampling without any phase jitter.

Water Vapor Profiling Using a Widely Tunable, Amplified Diode-Laser-Based Differential Absorption Lidar (DIAL)

Abstract A differential absorption lidar (DIAL) instrument for automated profiling of water vapor in the lower troposphere has been designed, tested, and is in routine operation at Montana State University. The laser transmitter for the DIAL instrument uses a widely tunable external cavity diode laser (ECDL) to injection seed two cascaded semiconductor optical amplifiers (SOAs) to produce a laser transmitter that accesses the 824–841-nm spectral range. The DIAL receiver utilizes a 28-cm-diameter Schmidt–Cassegrain telescope; an avalanche photodiode (APD) detector; and a narrowband optical filter to collect, discriminate, and measure the scattered light. A technique of correcting for the wavelength-dependent incident angle upon the narrowband optical filter as a function of range has been developed to allow accurate water vapor profiles to be measured down to 225 m above the surface. Data comparisons using the DIAL instrument and collocated radiosonde measurements are presented demonstrating the capabilities of the DIAL instrument.

Investigation on Characteristics and the Improving Method of Double Loop Optical Buffer

We establish an equivalent cascaded semiconductor optical amplifier system model to analyze the characteristics of the double loop optical buffer (DLOB). The theoretical analysis finds that the performance of the DLOB can be improved by inserted amplifying process in an interval of some cycles. The experiment demonstrates that the buffered cycles can be improved from 20 to 50 and the bit error rate is less than 10−9 by inserting amplifying process in an interval of about 10 cycles.

基于两只半导体光放大器级联结构的多波长光纤激光器

基于两只半导体光放大器级联结构的多波长光纤激光器