Performance Evaluation and Characterization of Hybrid Optical Amplifiers for Dwdm Systems at Ultra Narrow Channel Spacing

We study hybrid optical amplifiers (HOAs) for dense wavelength division multiplexed (DWDM) systems at reduced channel spacing (<0.2 nm). The Raman erbium-doped fiber amplifier (EDFA) (R-E) and EDFA-semiconductor optical amplifier (SOA) (E-S) hybrid optical amplifiers (HOAs) are investigated for the first time at 0.05 and 0.1 nm of the channel spacing. We show that the R-E HOA provides better gain (23.9 dB) and induces lesser crosstalk (-14.1 dB) with minimum utilization of the bandwidth. We report that 70 km is the optimum span distance at which the R-E HOA achieves a 2450 km transmission distance with acceptable performance. The theoretical results are found to be in accordance with numerical simulations in terms of the amplifier gain and induced crosstalk.     

Analytical Expressions of the Various Derivatives of the Output Power of the Semiconductor Optical Amplifiers with Respect to the Input Power

Based on the physical fact that the nonlinear distortions induced by the travelingwave semiconductor optical amplifiers in the subcarrier multiplexing CATV transmission system can be calculated by expressing the output power P o of the amplifiers with the Taylor series of the input optical power P i and specifying the various order derivatives of P o with respect to P i , the solutions to the rate equations of the amplifiers have been derived, and the analytical expressions of the various order derivatives of P o with respect to P i have been obtained and simulated numerically by selecting typical amplifier parameters.     

直接扣除法测量半导体光放大器频率响应

在光电子器件散射参量定义的基础上建立了基于直接扣除法的半导体光放大器频率响应测量系统,测量中通过扣除激光器和探测器系统的频率响应,得到放大器固有的频率响应。对InGaAsP体材料行波腔半导体光放大器样品进行了测量,得到了放大器在不同注入光功率和不同偏置电流下的频率响应曲线。这些曲线很好地反应了半导体光放大器的增益饱和和噪声特性,进一步分析发现半导体光放大器对低频调制信号的放大能力弱于对高频信号的放大能力,分析认为其原因在于半导体光放大器的载流子寿命有限导致低频信号长时间消耗载流子时,载流子数量无法及时恢复,从而使得增益降低。     

Enhancement of ring network in presence of optimized semiconductor optical amplifiers

By utilization of optimized semiconductor optical amplifiers, the design of ring network is achieved for a large number of nodes with reasonable quality and zero power penalty. The gain fluctuation occurs due to variation in parameters of the semiconductor optical amplifier for ring network. It is evaluated that nodes go on decreasing with increase in gain saturation of the semiconductor optical amplifier.     

Fundamentals of optical amplifiers

The minimum noise figure of linear phase-insensitive amplifiers is 3 dB, according to the constraint of the uncertainty principle. Laser amplifiers, parametric amplifiers and Raman amplifiers obey the general quantum limit in an ideal case. A degenerate parametric amplifier is a phase-sensitive linear amplifier, and thus is a noiseless amplifier with a noise figure of 0 dB. The noise figure degradation in a practical amplifier and the signal-to-noise ratio design of an optical amplifier system are presented. Several other amplifier characteristics, such as signal gain, frequency bandwidth and saturation output power, are also discussed.     

Control packet signaling mechanism using electronic code division multiple access for packet-based networks

We propose and experimentally demonstrate the feasibility of a control packet signaling technique using electronic code division multiple access for a wavelength division multiplexing packet-based network, whereby each wavelength channel is assigned a unique electronic code based label on a radio frequency subcarrier. Such a technique allows each wavelength channel to be electronically identified without requiring the use of a WDM demultiplexer. We experimentally demonstrate this technique with two wavelength channels each with 1.25 Gb/s baseband payload data and 10 Mb/s header coded onto an electronic code at 160 Mb/s. A performance study of the electronic code division multiple access based control signaling scheme in a wavelength division multiplexed packet-based access network is also performed in terms of the required power budget to monitor the electronic code division multiple access control signals in the presence of several sources of noise for error-free transmission of both payload data and electronic code division multiple access based control signals. It is shown that the modulation depth of each signal impacts the amount of required optical tap power. As the modulation depth of the electronic code division multiple access based control signal is increased, the required optical tap power is reduced. However, this increases the bit-error-rate for the payload data. Therefore, there lies a maximum and a minimum of the required tap optical power for the successful recovery of both signals. The lower bound of this range is usually determined by the successful recovery of electronic code division multiple access based control signal while the upper bound is determined by the successful recovery of payload data. The required optical tap power is analyzed for different transmission bit rates of the payload data for various receiver architecture scenarios without an optical amplifier at the receiver. The scalability analyses were repeated with an optical amplifier placed in the receiver terminal of the network. The resulting optical tap power that is required for the successful monitoring of the electronic code division multiple access based control signals are compared with that of the case without the amplifier.     

A CMOS Low-Power Optical Front-End for 5 Gbps Applications

In this paper, a new low-power optical receiver front-end is proposed in 90 nm CMOS technology for 5 Gb/s AApplications. However, to improve the gain-bandwidth trade-off, the proposed Trans-Impedance Amplifier (TIA) uses an active modified inverter-based topology followed by a common-source amplifier, which uses active inductive peaking technique to enhance the frequency bandwidth in an increased gain level for a reasonable power consumption value. The proposed TIA is analyzed and simulated in HSPICE using 90 nm CMOS technology parameters. Simulation results show a 53.5dBΩ trans-impedance gain, 3.5 GHz frequency bandwidth, 16.8pA/√Hz input referred noise, and 1.28 mW of power consumption at 1V supply voltage. The Optical receiver is completed using three stages of differential limiting amplifiers (LAs), which provide 27 dB voltage gain while consume 3.1 mW of power. Finally, the whole optical receiver front-end consumes only 5.6 mW of power at 1 V supply and amplifies the input signal by 80 dB, while providing 3.7 GHz of frequency bandwidth. Finally, the simulation results indicate that the proposed optical receiver is a proper candidate to be used in a low-power 5 Gbps optical communication system.     

Analytical Expressions of the Various Derivatives of the Output Power of the Semiconductor Optical Amplifiers with Respect to the Input Power

Based on the physical fact that the nonlinear distortions induced by the travelingwave semiconductor optical amplifiers in the subcarrier multiplexing CATV transmission system can be calculated by expressing the output power P o of the amplifiers with the Taylor series of the input optical power P i and specifying the various order derivatives of P o with respect to P i , the solutions to the rate equations of the amplifiers have been derived, and the analytical expressions of the various order derivatives of P o with respect to P i have been obtained and simulated numerically by selecting typical amplifier parameters.     

半导体光放大器引起的串扰及其抑制技术

由于半导体光放大器(SOA)的增益饱和效应,在波分复用系统中.每个信道的增益受到复用的其它信道的影响.SOA引起的各信道之间的串扰严重限制了其应用.理论研究了SOA增益饱和效应引起的信道间串扰.数值模拟了多路信道复用时系统的误码率随复用信道数和光功率的变化情况,发现随着复用信道数的增加SOA增益饱和引起的信道间串扰越来越严重.对SOA中串扰的抑制方法进行了理论和实验研究.数值模拟发现连续光注入可以抑制输出功率的波动,从而减小误码率,当复用10个信道时,连续光注入可以使功率代价减小2 dB;实验验证了两信道的40 Gb/s系统中,注入连续光可以减少SOA引起的信道间串扰.     

抽运方式对混合拉曼光纤放大器性能的影响

通过实验比较了前向抽运拉曼光纤放大器与掺铒光纤放大器组成的混合放大器、后向抽运拉曼光纤放大器与掺铒光纤放大器组成的混合放大器的性能。实验采用75km标准单模光纤作为增益介质。采用20信道(符合ITU-T建议的波分复用信号)，波长为1537．377～1560．605nm，作为混合放大器的测试信号。20信道总功率-2．86dBm，每一信道用2．5Gb／s、码长2^7-1的非归零码通过电吸收调制器(EA)进行外调制。实验结果表明，前向抽运方式混合放大器的性能优于后向抽运方式的混合放大器，其中噪声系数的改善值为2．28～6．55dB。采用前向抽运时，各信道的增益同后向抽运相比，增加值均大于5dB。但不论采取那种抽运方式，采用混合放大的形式，各信道的光信噪比均大于26．9dB。     

Transverse Bragg resonance laser amplifier

We propose and analyze a new type of optical amplifier that is formed by addition of gain in the periodic cladding of a transverse Bragg resonance waveguide [Opt. Lett. 27, 936 (2002)]. Using the coupled-wave formalism, we calculate the mode profiles, the exponential gain constant, and, for comparison, the gain enhancement compared with those of conventional semiconductor optical amplifiers. In contrast with coupled-mode theory, in one-dimensional structures (e.g., the distributed-feedback laser) the exponential gain constant in the longitudinal direction is involved in both longitudinal and transverse confinement, and its solution has to be achieved self-consistently, together with the quantized guiding channel width.     

Dynamic-channel-equalizer using in-line channel power monitor and electronic variable optical attenuator

We propose and demonstrate a polarization-insensitive dynamic-channel-equalizer (DCE) for compensating erbium-doped-fiber-amplifier (EDFA) amplified signals after dynamic optical add/drop. The DCE can be monolithically integrated on silicon-on-insulator (SOI) platform and is potentially low cost and compact. The DCE can compensate complicated gain slope shape, which may be generated in cascaded EDFAs or deliberate channel add/drop, based on individual channel equalization. Fifteen-decibel receiver sensitivity improvement at 10 Gb/s bit-error-rate (BER) measurement of 10⁻⁹ was achieved in the compensated channel by removing cross-gain-modulation generated by neighboring channel add/drop.     

基于垂直谐振腔结构的半导体光放大器理论分析

由新型垂直腔半导体光放大器（VCSOAs）器件结构出发,在反射模式和透射模式两种 情况下,计算了VCSOAs的分布布拉格反射堆（DBR）反射率、单程增益与增益、带宽的关系 ,其中DBR反射率的增大伴随着增益的上升,但也伴随着带宽的减小.通过引入增益-带宽 积的概念,以均衡增益与带宽.计算中表明:10 dB以上增益,50 GHz以上带宽可以实现. 计算结果与文献实验相吻合,对优化VCSOAs的结构设计和性能有所裨益.     

Beam deflection and isolation in laser amplifiers

A new beam deflection and collimation technique is described which utilizes transverse gain variations in laser amplifiers. This method may be used to achieve beam mixing or optical isolation between the stages of an amplifier chain. Results with a CO₂ amplifier are decribed.     

Multiple-Output Fiber-Ring Lasers and Amplifiers in a Hybrid CATV and ADSL Broadcasting Optical Fiber Communication System

In this article we propose two kinds of new fiber ring structure with a semiconductor optical amplifier. The first structure is a one-fiber-ring amplifier with an 8 × 8 fiber coupler and a semiconductor optical amplifier (SOA). The second fiber ring structure is a two-fiber-ring laser including an 8 × 8 fiber coupler, a 2 × 2 E/O modulator, and an SOA. The 14-output spectra of the fiber laser are measured. The gain coefficients of each port of the multiple-output-fiber-ring amplifiers are also measured. We apply these two kinds of fiber ring structures in a hybrid CATV and ADSL broadcasting optical fiber communication system. This application can develop a broadcasting system with large coverage area without using many laser diodes and optical amplifiers. The performance of such a system is also analyzed in this article.     

Continuous-Variable Quantum Key Distribution Based on Heralded Hybrid Linear Amplifier with a Local Local Oscillator

An improved continuous variable quantum key distribution (CVQKD) approach based on a heralded hybrid linear amplifier (HLA) is proposed in this study, which includes an ideal deterministic linear amplifier and a probabilistic noiseless linear amplifier. The CVQKD, which is based on an amplifier, enhances the signal-to-noise ratio and provides for fine control between high gain and strong noise reduction. We focus on the impact of two types of optical amplifiers on system performance: phase sensitive amplifiers (PSA) and phase insensitive amplifiers (PIA). The results indicate that employing amplifiers, local local oscillation-based CVQKD systems can enhance key rates and communication distances. In addition, the PIA-based CVQKD system has a broader application than the PSA-based system.     

Multiple-Output Fiber-Ring Lasers and Amplifiers in a Hybrid CATV and ADSL Broadcasting Optical Fiber Communication System

In this article we propose two kinds of new fiber ring structure with a semiconductor optical amplifier. The first structure is a one-fiber-ring amplifier with an 8 × 8 fiber coupler and a semiconductor optical amplifier (SOA). The second fiber ring structure is a two-fiber-ring laser including an 8 × 8 fiber coupler, a 2 × 2 E/O modulator, and an SOA. The 14-output spectra of the fiber laser are measured. The gain coefficients of each port of the multiple-output-fiber-ring amplifiers are also measured. We apply these two kinds of fiber ring structures in a hybrid CATV and ADSL broadcasting optical fiber communication system. This application can develop a broadcasting system with large coverage area without using many laser diodes and optical amplifiers. The performance of such a system is also analyzed in this article.     

A novel approach to all-optical wavelength conversion by utilizing a reflective semiconductor optical amplifier in a co-propagation scheme

Nonlinear optical gain modulation in an InGaAsP/InP bulk reflective semiconductor optical amplifier (RSOA) is studied. The differences of the optical properties between RSOAs and conventional SOAs are initially investigated. All-optical wavelength conversion based on nonlinear gain modulation in RSOAs is demonstrated at a bit rate of 2.488 Gbit/s. It is shown that a bit-error-rate of <10⁻⁹ can be achieved and an extinction ratio of >9 dB can be obtained at a bit rate of 2.488 Gbit/s with a 2³¹-1 non-return-to-zero (NRZ) pseudorandom bit sequence (PRBS). In comparison with conventional SOAs, wavelength conversion by RSOAs shows much improved performances in high-speed all-optical wavelength conversions.     

An optical discrimination amplifier

Measurements on an optical discrimination amplifier are presented which demonstrate its ability to increase the S/N ratio of single ultrashort pulses by 2 to 3 orders of magnitude. The amplifier consists of a series of amplifiers and dye cells such that for each dye-amplifier section the small-signal gain is less than one.