Optical System with two packaged 1.5 ?m semiconductor laser amplifier repeaters

The first demonstration of two packaged 1.5 ?m semiconductor laser amplifiers in an optical system is reported. Total coupling losses for the fibre-tailed packages were 10dB and 13 dB, respectively. In a 140 Mbit/s intensity-modulated system experiment, using the amplifiers as linear repeaters, a total repeater again of 26 dB was achieved.     

Sea trial of submarine optical amplifier repeater system using travelling-wave semiconductor laser amplifier

An optical amplifier repeater system consisting of semiconductor laser amplifiers was evaluated in 3000 m deep sea at 820 Mbit/s in the 1.5 mu m wavelength region using 23.5 km of optical submarine cable. The repeater output power was stabilised by an APC system monitoring amplified optical signal power. The authors confirmed stable digital signal transmission and the reduction of variation in the repeater output power for changes in the polarisation of the input signal.<>     

Traveling wave semiconductor laser amplifier detectors

Near-traveling-wave semiconductor laser amplifiers for amplification and detection of optical signals are discussed. Measurements of gain, responsivity, and bandwidth are presented and compared with theory. The system performance of the laser amplifier detector is evaluated by a digital transmission experiment. The importance of using low-reflectivity amplifiers with high-responsivity and weakly wavelength-dependent devices is revealed by computer simulations. The various noise contributions of the laser amplifier detector are analyzed. Expected sensitivity values are given, and it is shown that there exists an optimum amplifier gain with respect to sensitivity     

Improvement of cascaded semiconductor optical amplifier gates byusing holding light injection

The cascadability of semiconductor optical amplifier (SOA) gates by using holding light injection is numerically and experimentally investigated. Our experimental results show that the signal bit error rate after two cascaded SOA gates will be larger than 10^-9 without holding light injection; however 11 SOA gates can be cascaded with holding light injection. The results show that the number of cascaded SOA gates by using holding light injection can be strongly increased     

Four-wave mixing in travelling-wave semiconductor laser amplifier

Experiments on codirectional nondegenerate four-wave mixing in a 1.52 mu m travelling-wave semiconductor laser amplifier are presented. Estimations for the spontaneous carrier lifetime and linewidth enhancement factor are derived from comparison between experimental and calculated results from theory based on signal-induced carrier-density modulation.<>     

Four-wave mixing in a semiconductor laser amplifier

Reports on nearly degenerate four-wave mixing (NDFWM) of two copropagating light waves inside a travelling wave amplifier (1.3 μm) at input light powers of less than 10 μW. It describes the first experimental determination of the range of frequency spacing of the two light waves for efficient NDFWM and of the dependence on the state of polarisation     

Noise in an AlGaAs semiconductor laser amplifier

The noise characteristics in a Fabry-Perot (FP) cavity type semiconductor laser amplifier, biased at just below its oscillation threshold current, have been studied theoretically and experimentally. Quantum mechanical multimode rate equations containing a Langevin shot noise source and an input signal term were numerically solved for an exponential band-tail model with nok-selection rule. Noise power calculated using this rate equation was compared with a simpler photon statistic master equation method. The experimental results on noise power for an AlGaAs laser amplifier are in reasonable agreement with the two different theoretical predictions. Dominant noise powers in a semiconductor laser amplifier are beat noise powers between signal and spontaneous emission, and between spontaneous emission components. Noise characteristics in a Fabry-Perot cavity type laser amplifier can be improved both by the reduction of the facet mirror reflectivities and by use of an asymmetric cavity configuration with low-input and high-output mirror reflectivities. Two beat noise powers are expressed in simple analytic form by introducing an equivalent noise bandwidth and an excess noise coefficient as figures of merit in an optical amplifier.     

Optical loop mirror with semiconductor laser amplifier

A nonlinear optical loop mirror is reported, employing a semiconductor laser amplifier (SLA). The input-output characteristic is distinctly nonlinear, and when operating as an optical correlator, an extinction ratio of 13 dB was achieved.<>     

A wide-band limiting amplifier for optical fiber repeaters

An integrated amplifier having a bandwidth of 470 MHz, and a gain and limiting range of 60 dB has been realized using a cascade of three cells on an uncommitted array. The circuit is capable of operating in optical fiber repeaters in the signal or retiming path at transmission rates up to 650 MBd. Direct expressions for calculating the gain and bandwidth have been derived which allow optimization of the component values, bias conditions, and transistor parameters for a chosen application.     

1.3μm行波式半导体激光放大器

利用多级尝试法对主动监控法进行优化,获得了两端面剩余模式反射率几何平均值小于3×10-4的行波式半导体激光放大器,并在1.3μm波段获得了20dB的信号增益。     

Picosecond semiconductor laser radar with optical amplifier

An optical range finder, which uses the same semiconductor laser as both an optical pulse source and an optical preamplifier of the reflected pulse, is reported. This method has the advantage of reducing the number of optical components that must be aligned, which makes it suitable as a picosecond laser radar in aerospace applications. The device showed a maximum optical gain of 17 dB with a dynamic range of 33 dB, and the obtained resolution was of the order of 1 mm.     

1.3 mu m semiconductor laser power amplifier

The performance of a 3.4-Gb/s system using a low-power 1.318- mu m distributed-feedback (DFB) laser transmitter and a traveling-wave semiconductor laser power amplifier is studied. The -14.5-dBm, input from a directly modulated DFB laser is boosted to +10.3 dBm, of which +4.8 dBm is coupled into the transmission fiber. The penalty, caused by amplifier noise and pattern effects due to gain saturation, is less than 0.5 dB.<>     

Measurement of semiconductor laser amplifier noise figure in coherent optical transmission system

Reports the first detailed investigation of the effect of semiconductor laser amplifier noise figure on the sensitivity of a heterodyne receiver. Independent measurement of the amplifier spontaneous noise spectral density confirms that local oscillator-spontaneous emission beat noise accounts for all of the observed penalty.<>     

WDM-PON system based on the laser light injected reflective semiconductor optical amplifier

This paper proposes a WDM-PON system which uses the laser light injected reflective semiconductor optical amplifier (R-SOA) as the optical transmitter. In the system, optical carrier of laser lights is supplied from the central office (CO) to the R-SOA both in CO and in the subscriber's side. The optical carrier consists of a pair of the perpendicularly polarized laser lights to avoid the polarization dependence of R-SOA. The optical carrier can be shared by several WDM-PON systems to save the cost. We measured the transmission performance of R-SOA which modulates the polarization mixed injection laser at 1.25 Gbps. It is shown that the combined effect of Rayleigh backscattering and the intensity noise induced by the feedback of optical signals into the R-SOA increases the required level of optical injection power into the R-SOA.     

IL型半导体激光放大器的噪声

IL型激光放大器(LA)可以用做光功率放大器,也可以用做中继放大器代替复杂的光-电中继器.IL型LA的噪声性能对相干光通信系统的性能至关重要,它直接影响到系统的误码率.我们对IL型LA的强度噪声谱和频率飘移谱,进行了数值计算,并讨论了注入光的噪声谱、注入光功率和锁定相位等对噪声谱的影响.     

Optical time-domain reflectometer with a semiconductor laser amplifier

An optical time-domain reflectometer (OTDR) using a semiconductor laser as an optical pulse generator and as a back-scattered optical signal amplifier is reported. It is found that the detectable one-way loss of the apparatus is improved by 4.5 dB compared with the conventional OTDR using direct detection.     

Performance analysis on semiconductor laser amplifier loop mirrors

Operating characteristics of the semiconductor laser amplifier loop mirror (SLALOM) in optical time-division multiplexing (OTDM) applications are investigated in theory. The injection current of the semiconductor laser amplifier (SLA) should be adjusted to realize a flat and high switching window. The channel crosstalk induced by the finite carrier lifetime and the signal timing jitter should be balanced. The optimal switching window width should be slightly wider than half of the OTDM signal bit interval. The control pulse should be narrower than one-third of the OTDM bit interval in order not to deteriorate the bit error rate (BER) performance. Further discussion indicates that the nonlinear gain compression in the SLA becomes a crucial limit for the SLA-based all-optical switches to be used in the terahertz applications     

Polarisation characteristics of a travelling-wave-type semiconductor laser amplifier

We report experimental results on the gain sensitivity of a travelling-wave-type (TW) AlGaAs semiconductor laser amplifier to the input signal polarisation state.     

Chirp compensation capability of a semiconductor laser amplifier

Performance improvement is reported resulting from incorporating a semiconductor laser amplifier (SLA) as a post-transmitter-amplifier in long-haul directly modulated optical systems operating in the 1.5 mu m region. This improvement arises from reduction of the chirp produced by the semiconductor laser as the signal passes through the SLA. Eye closure penalty improvements in excess of 5 dB are observed for an illustrative long-haul 4.8 Gbit/s system.<>