Impact of dispersion, PMD, and PDL on the performance of spectrum-sliced incoherent light sources using gain-saturated semiconductor optical amplifiers

The effects of chromatic dispersion (CD), polarization-mode dispersion (PMD), and polarization-dependent loss (PDL) on the intensity noise suppression of spectrum-sliced incoherent light sources achieved by using gain-saturated (GS) semiconductor optical amplifiers (SOAs) are investigated. Passing the spectrum-sliced incoherent light through SOAs, the excess intensity noise (EIN) originating from beating of spontaneous emission against itself can be greatly reduced. However, since the noise suppression is achieved by an elaborate balancing between numerous frequency/polarization components of light, thus, forming a high correlation between them, it is vulnerable to frequency/polarization-dependent optical phenomena. Through Q-factor and bit error rate (BER) measurements, this paper shows that CD, PMD, or PDL deteriorates the SOA-based noise suppression technique by breaking the correlation. Spectral analysis is also performed to investigate the frequency dependency of these effects. It is shown that CD and PMD negate the noise suppression giving rise to intensity noise from high frequencies, whereas there is no frequency dependence for PDL effects. Therefore, CD-, PMD-, or PDL-induced penalties for incoherent light sources using the SOA-based noise suppression technique are considerably greater than those produced by pulse broadening or distortion alone.     

Improving the all-optical response of SOAs using a modulated holding signal

A method for increasing the all-optical modulation bandwidth of semiconductor optical amplifiers (SOAs) by use of a cross-gain-modulated (XGM) holding signal is suggested and analyzed. The bandwidth improvement is numerically demonstrated by studying wavelength conversion in an SOA-based Mach-Zehnder interferometer (MZI) at 160 and 40 Gb/s. The new scheme is predicted to improve the extinction ratio and the minimum mark output power, as well as to reduce the amplitude jitter of the wavelength converted signal.     

Nonlinear Polarization Rotation in Semiconductor Optical Amplifiers With Linear Polarization Maintenance

We propose a geometrical model based on the concept of dynamic eigenstates of polarization to describe the behavior of nonlinear polarization rotation (NPR) arising in semiconductor optical amplifiers (SOAs). The rotation axis with respect to either the bias current or the optical power variation is demonstrated on the Poincare sphere (PS), meanwhile a procedure to find the rotation axis is presented. Thus, the SOA-based NPR with linear polarization maintenance (zero polarization ellipticity angle) can be achieved experimentally. The rotation of polarization azimuth on the PS with respect to the bias current, the probe signal power, and the pump signal power variation is measured experimentally. The 180deg phase difference between the transverse electric and the transverse magnetic modes can be all achieved with linear polarization maintenance.     

Effects of intraband crosstalk on incoherent light using SOA-based noise suppression technique

We investigate the effects of intraband crosstalk on the intensity noise suppression of spectrum-sliced incoherent light sources using semiconductor optical amplifiers (SOAs). Both Q-factor and electrical spectrum measurements clearly show that intraband crosstalk deteriorates the SOA-based noise suppression by breaking the correlation between optical frequency components of light.     

WDM-POLSK Transmission Systems by Using Semiconductor Optical Amplifiers

The authors demonstrate the potential of using POLarization Shift Keying (POLSK) modulation format combined with semiconductor optical amplifiers (SOAs) in wavelength division multiplexing (WDM) transmission systems. The constant intensity of the POLSK modulation format allows for substantial removal of cross-gain-modulation impairments in SOAs so that practical amplifier spacing values (more than 100 km) are demonstrated in various different experimental configurations. Record WDM transmission experiments at 10 Gb/s by using SOA-based amplification are presented in short and medium reach system architectures using either single mode fiber or nonzero dispersion shifted fiber     

A Mach-Zehnder-interferometer-based low-loss combiner

Passive optical combiners have an unwanted 3-dB loss. This is avoided with optical switches, but these need control functions to synchronize with the optical signals. A nonlinear Mach-Zehnder interferometer can provide the combiner function without control signals. In the experiment reported here, this combiner was realized with a fiber component. Semiconductor optical amplifiers (SOAs) acted as the nonlinear phase shifting elements. Thus a proof-of-principle for the self-routing combiner is obtained: optical signals on either of the two input ports are guided to one and the same output port without any control mechanism in the interferometer. The nonlinear effect used is self-phase modulation, caused by carrier depletion in the SOAs as they approach saturation. The optical power at which the nonlinear switching occurred was about -2 dBm. The residual combiner loss was only 0.7 dB     

High-Speed Mode-Locked Quantum-Dot Lasers and Optical Amplifiers

Recent results on GaAs-based high-speed mode-locked quantum-dot (QD) lasers and optical amplifiers with an operation wavelength centered at 1290 nm are reviewed and their complex dependence on device and operating parameters is discussed on the basis of experimental data obtained with integrated fiber-based QD device modules. Hybrid and passive mode locking of QD lasers with repetition frequencies between 5 and 80 GHz, sub-ps pulse widths, ultralow timing jitter down to 190 fs, high output peak power beyond 1 W, and suppression of Q-switching are reported, showing the large potential of this class of devices for O-band optical fiber applications. Results on cw and dynamical characterization of QD semiconductor optical amplifiers (SOAs) are presented. QD amplifiers exhibit a close-to-ideal noise figure of 4 dB and demonstrate multiwavelength amplification of three coarse wavelength division multiplexing (CWDM) wavelengths simultaneously. Modelling of QD polarization dependence shows that it should be possible to achieve polarization insensitive SOAs using vertically coupled QD stacks. Amplification of ultrafast 80 GHz optical combs and bit-error-free data signal amplification at 40 Gb/s with QD SOAs show the potential for their application in future 100 Gb Ethernet networks.     

All-optical signal processing based on semiconductor optical amplifiers

In this paper,we review the recent progress in the optical signal processing based on the nonlinearity of semiconductor optical amplifiers (SOAs).The four important optical signal processing functional blocks in optical switching are presented,i.e.,optical wavelength conversion,optical regeneration,optical logic,and optical format conversion.We present a brief overview of optical wavelength conversion,and focus on various schemes to suppress the slow gain recovery of the SOA and improve the operating speed of the SOA-based optical switches.Optical regeneration including re-amplification,re-shaping and re-timing is also presented.Optical clock recovery that is essential for optical regeneration is reviewed.We also report the recent advances in optical logic and optical format conversion,respectively.After reviewing the four important optical signal processing functional blocks,the review concludes with the future research directions and photonic integration.     

Using Semiconductor-Optical Amplifiers With Constant Envelope WDM Signals

Semiconductor-optical amplifiers (SOAs) could be used in wavelength-division multiplexing (WDM) systems with constant envelope modulation formats. However if chromatic dispersion affects their constant envelope, WDM signals can interact via the SOA carrier density fluctuations, resulting into relevant penalty. We experimentally and theoretically investigate the operating conditions for SOA-based amplification with DPSK and POLSK modulation formats and clarify the role of input power, residual dispersion and modulation format. We also determine that, for a given format, the various detection schemes can result into very different impairments. These results can be used as guidelines for the system design.     

Transmission performance of 10-Gb/s 1550-nm transmitters using semiconductor optical amplifiers as booster amplifiers

We have demonstrated the transmission performance of 10-Gb/s transmitters based on LiNbO/sub 3/ modulator using semiconductor optical amplifiers (SOAs) as booster amplifiers. Utilizing the negative chirp converted in SOAs and self-phase modulation induced by high optical power, we can successfully transmit 10-Gb/s optical signals over 80 km through the standard single-mode fiber with the transmitter using SOAs as booster amplifiers. SOAs can be used for booster amplifiers with a careful adjustment of the operating conditions. In order to further understand an SOA's characteristics as a booster amplifier, we model SOAs and other subsystems to verify the experimental results. Based on the good agreement between the experimental and simulation results, we can find the appropriate parameters of input signals for SOAs, such as extinction ratio, rising/falling time, and chirp parameter to maximize output dynamic range and available maximum output power (P/sub o,max/).     

Hybrid material integration in silicon photonic integrated circuits

Hybrid integration ofⅢ-Ⅴand ferroelectric materials is being broadly adopted to enhance functionalities in silicon photonic integrated circuits(PICs).Bonding and transfer printing have been the popular approaches for integration of III–V gain media with silicon PICs.Similar approaches are also being considered for ferroelectrics to enable larger RF modulation bandwidths,higher linearity,lower optical loss integrated optical modulators on chip.In this paper,we review existing integration strategies ofⅢ-Ⅴmaterials and present a route towards hybrid integration of bothⅢ-Ⅴand ferroelectrics on the same chip.We show that adiabatic transformation of the optical mode between hybrid ferroelectric and silicon sections enables efficient transfer of optical modal energies for maximum overlap of the optical mode with the ferroelectric media,similar to approaches adopted to maximize optical overlap with the gain section,thereby reducing lasing thresholds for hybridⅢ-Ⅴintegration with silicon PICs.Preliminary designs are presented to enable a foundry compatible hybrid integration route of diverse functionalities on silicon PICs.     

An Adjustable Gain-Clamped Semiconductor Optical Amplifier (AGC-SOA)

The operation of a semiconductor optical amplifier (SOA)-ring laser-based subsystem, with the capability to provide adjustable gain-clamped operation, will be described, and preliminary characterization results will be presented. The device uses two SOAs in a ring-cavity topology: one to amplify the signal and the other to control the gain. This type of subsystem finds applications in packet-based dynamic systems where it may be used for power equalization and linear amplification.     

半导体光放大器的增益透明电流测量方法研究

半导体光放大器(SOA)作为全光集成器件的核心,在全光通信和光纤传感等领域中具有重要的应用前景。值得关注的是,半导体光放大器的材料增益透明决定了它的快慢光过渡点和信号增益的起始点,因此准确测量其材料增益透明对应的注入电流,对于SOA的全面应用具有重要意义。提出了一种测量SOA材料增益透明电流的方法,并深入分析了其特点。依据材料增益透明时SOA的输出功率与入射光偏振无关的特性,实验测量了不同输入光功率条件下,入射光偏振态对输出功率影响最小时,SOA的注入电流。利用上述方法,准确地测量出给定波长输入待测SOA的增益透明电流为155mA。该方法为实现其他类型任意波长注入时SOA增益透明电流的测量提供了参考,为其全面应用奠定了基础。     

High-power 1.5-/spl mu/m InGaAsP-InP slab-coupled optical waveguide amplifier

We report the first demonstration of a high-power semiconductor optical amplifier (SOA) based on the slab-coupled optical waveguide concept. This concept allows the realization of SOAs having large fundamental optical modes, low loss, and small optical confinement factor. These attributes support large output saturation power, long length for efficient heat removal, and direct butt-coupling to single-mode fibers. The 1.5-/spl mu/m InGaAsP-InP quantum-well amplifier described here has a length of 1 cm, 1/e/sup 2/ intensity widths of 4 /spl mu/m (vertical) and 8 /spl mu/m (horizontal), a fiber-to-fiber gain of 13 dB, and a fiber-coupled output saturation power of 630 mW (+28 dBm). The measured butt-coupling efficiency between the amplifier and SMF-28 is 55%. Thus, the output saturation power of the amplifier itself is approximately 1.1 W (+31 dBm).     

基于两只半导体光放大器级联结构的多波长光纤激光器

通过数值模拟对两只半导体光放大器(SOA)级联结构的静态增益饱和特性进行了理论研究.在不考虑自发辐射的情况下,分析了注入电流对两只SOA级联结构增益的影响.实验上构建了一种基于两只SOA级联结构的多波长光纤激光器,观测并分析了半导体光放大器的驱动电流和增益带宽对多波长输出结果的影响.在室温下,获得了基本符合ITU-T标准100 GHz的27个波长以上的稳定多波长输出,各信道输出功率不平坦度小于±3 dB,线宽小于0.102 nm,信噪比大于25 dB,总输出功率为1.94 mW,并且与由单只SOA构成的多波长光纤激光器进行了对比.     

Extremely fast high-gain and low-current SOA by optical speed-up at transparency

We propose a new configuration for semiconductor optical amplifiers (SOAs), called optical speed-up at transparency (OSAT), which allows to speed up the gain recovery of SOAs and their saturation power without sacrificing the gain, nor increasing the applied current. The proposed configuration is particularly well-suited for high-speed WDM or OTDM applications. It consists of an optical CW-signal injected at the transparency point of the SOA. This setup is potentially integrable on a single chip, and still relatively flexible once the device is realized.     

Generation of an ultra-wideband triplet signal based on semiconductor optical amplifier

We propose a novel ultra-wideband (UWB) triplet signal source based on the cross-gain modulation (XGM) in semiconductor optical amplifier (SOA). In the proposed scheme, only an optical source and two SOAs are needed, so the all-optical structure is compact. A triplet optical pulse with center frequency of 6.25 GHz and fractional bandwidth of 83% is obtained by the scheme. The extinction ratio can be improved by the counter-propagating scheme. The triplet pulse signal with only one wavelength can be easily controlled, and can aviod the dispersion effect. The output triplet pulse signal is insensitive to the light wavelength shifts, its available wavelength range is wide, the dynamic range of the input power is more than 6 dBm, and the bias current of the SOAs is exhibited.     

First demonstration of simultaneous demultiplexing from 40 Gbit/sinto two channels of 20 Gbit/s by SOA-based all-optical polarisationswitch

Simultaneous demultiplexing from 40 Gbit/s data signal into two channels of 20 Gbit/s using semiconductor optical amplifier (SOA) based all-optical polarisation switch has been demonstrated. Error-free operation was confirmed with no power penalty. This is the first experimental demonstration to prove the full-switching capability of the SOA-based Mach-Zehnder interferometer (MZI) all-optical switch at such a high bit rate regime     

Measurements and Simulations of nonlinear noise redistribution in an SOA

Measurements and numerical simulations of the noise statistics after a semiconductor optical amplifier (SOA) demonstrate nonlinear noise redistribution. The redistribution, which relies on self-modulation due to gain saturation and carrier dynamics, shows a strong power and bandwidth dependence and can be important for SOA-based regenerators.     

全光波长转换器噪声变换的小信号分析方法

本文利用小信号模型对基于半导体光放大器（SOA）交叉增益调制（XGM）波长转换器的噪声变换进行了理论分析和数据计算,结果表明,泵浦光功率和探测光功率的大小以及光放大器的增益对噪声变换有直接的影响,在适度的输入功率范围内,噪声得到了有效的抑制。