Picosecond optical pulse compression from gain-switched 1.3 ?m distributed-feedback laser diode through highly dispersive single-mode fibre

The first demonstration to compress the linearly chirped optical pulses from a gain-switched distributed-feedback laser diode (DFB-LD) is described at 1.3 ?m wavelength. By travelling through a highly dispersive single-mode fibre with 48 ps/nm normal dispersion, a 26 ps (FWHM) pulse having red-shift frequency chirping of 85 GHz (FWHM) is compressed to 8.3 ps with the time-bandwidth product of 0.71.     

Generation of <3 ps optical pulses by fibre compression of gain-switched InGaAsP DFB laser diode pulses

Generation of <3 ps full width at half maximum (FWHM) 1.3 mu m pulses by compressing the chirped output of a gain-switched distributed feedback laser diode (DFB-LD) with a fibre dispersive delay line is reported. Diode laser requirements for minimum pulse width and maximum pulse energy, as well as suppression of 'wings' on the optical pulse, are discussed.<>     

Nonlinear interaction between optical pulses from high-repetition gain-switched DFB-LD in optical fiber

Interaction forces between propagating pulse pairs from a gain-switched distributed feedback laser diode (DFB-LD) were investigated. The authors discuss the experimental observation of a nonlinear interaction force between the fiber-compressed, gain-switched optical pulses. Optical pulses were generated by a gain-switched 1.55 mu m DFB-LD at a 10 GHz repetition rate, and compressed by compensating for the red-shifted chirping in the optical pulses using a polarization-holding fiber with a 18.7 ps/km/nm normal dispersion at a 1.55 mu m wavelength. The measured interaction force, which was greater than that theoretically predicted, was caused by the wings and/or pedestal associated with copropagating pulses.<>     

Transform-limited 5.6 ps optical pulse generation at 12 GHz repetition rate from gain-switched distributed feedback laser diode by employing pulse compression technique

12 GHz chirped optical pulses from a gain-switched 1.3 ?m distributed feedback laser diode are compressed to transform-limited 5.6 ps pulses by travelling through a dispersion shifted single-mode fibre with 46 ps/nm normal dispersion. A time-bandwidth product of 0.69 and a high on/off ratio of 20 dB are obtained for optimally compressed pulses.     

Simultaneous mode selection and pulse compression of gain-switchedpulses from a Fabry-Perot laser using a 40-mm chirped optical fibergrating

Simultaneous pulse compression and mode selection of gain-switched pulses from a Fabry-Perot semiconductor laser are demonstrated using a chirped optical fiber Bragg grating, which has transformed initially chirped 60-ps pulses from an inexpensive multimode laser into a train of 12-ps single-mode pulses with a side-mode suppression ratio of 15.2 dB     

Demonstration of chirping manipulation of laser diode chirped optical pulses utilising cross-phase modulation in optical fibres

A new method to manipulate the chirp characteristics of laser-diode pulses is proposed, utilising the cross-phase modulation in optical fibres. Chirping manipulation of a red-shift chirped pulse from a 1.3 mu m gain-switched distributed-feedback laser diode is first demonstrated by compensating for the residual chirp through the blue-shift chirp induced by a 1.3 mu m intense YAG pump pulse.<>     

A high-speed optical star network using TDMA and all-opticaldemultiplexing techniques

The authors demonstrate the use of time-division multiplexing (TDM) to realize a high capacity optical star network. The fundamental element of the demonstration network is a 10 ps, wavelength tunable, low jitter, pulse source. Electrical data is encoded onto three optical pulse trains, and the resultant low duty cycle optical data channels are multiplexed together using 25 ps fiber delay lines. This gives an overall network capacity of 40 Gb/s. A nonlinear optical loop mirror (NOLM) is used to carry out the demultiplexing at the station receiver. The channel to be switched out can be selected by adjusting the phase of the electrical signal used to generate the control pulses for the NOLM. By using external injection into a gain-switched distributed feedback (DFB) laser we are able to obtain very low jitter control pulses of 4-ps duration (RMS jitter <1 ps) after compression of the highly chirped gain switched pulses in a normal dispersive fiber. This enables us to achieve excellent eye openings for the three demultiplexed channels. The difficulty in obtaining complete switching of the signal pulses is presented. This is shown to be due to the deformation of the control pulse in the NOLM (caused by the soliton effect compression). The use of optical time-division multiplexing (OTDM) with all-optical switching devices is shown to be an excellent method to allow us to exploit as efficiently as possible the available fiber bandwidth, and to achieve very high bit-rate optical networks     

Analysis of optical phase-conjugate characteristics of picosecondfour-wave mixing signals in semiconductor optical amplifiers

We have analyzed for the first time the optical phase-conjugate characteristics of picosecond four-wave mixing (FWM) signals in semiconductor optical amplifiers (SOAs) using the finite-difference beam propagation method (FD-BPM). We show that the optical phase-conjugate characteristics of the FWM signals are strongly dependent on input pump pulsewidths. As a typical example, we have demonstrated that SOAs act as an ideal phase-conjugator, within the confines of reversing the chirp of optical pulses, for a 10-ps input pump pulse and a ~2.2-ps linearly chirped input probe pulse. When the pulsewidth of pump pulse becomes short, the minimum compressed pulsewidth is obtained by using a fiber shorter in length than the input fiber, but having the same group velocity dispersion as the input fiber. For a much shorter pump pulse such as 1 ps, the short FWM signal can be obtained via the gating characteristics of the FWM. However, only a part of the phase information is copied to the FWM signal due to such gating characteristics. The phase information is also degraded due to the fast nonlinear effect in the SOA. Thus, the pulsewidth is not compressed by propagation through a dispersive medium     

光纤中双脉冲传输的频率啁啾及脉冲压缩

对双脉冲在光纤中传输时所满足的非线性耦舍方程进行了理论分析和数值计算,求得了脉冲演化时啁啾参量的一般表达式。结果表明,利用交叉相位调制效应压缩光脉冲时,无论泵浦脉冲还是信号脉冲,其线性源啁啾都对光脉冲的压缩产生重要影响。在泵浦功率一定的条件下,选取负啁啾的泵浦脉冲和正啁啾的信号脉冲易于获得更短的压缩光脉冲。     

Smoothly wavelength-tunable picosecond pulse generation using a harmonically mode-locked fiber ring laser

A simple design of a stable, smoothly wavelength-tunable picosecond pulse generator has been demonstrated using a dispersion-tuned, harmonically mode-locked fiber ring laser with a directly modulated semiconductor optical amplifier (SOA). The SOA functions as both a polarization-insensitive mode locker and a supermode noise suppressor. Near-linearly chirped pulses are generated and compressed to less than 4 ps when the intracavity dispersion is anomalous while 11-ps, near-transform-limited pulses are generated without compression when the dispersion is normal. Smooth wavelength tuning is achieved over more than 11 nm by only tuning the modulation frequency and pulse characteristics are stable over the entire tuning span. A simple numerical model successively simulates the operation principle of the system. The tuning range is determined by both the gain profile and the total intracavity dispersion. The dispersion and the SOA ensure the long-term stability of the system.     

160 Gb/s sub-picosecond transform-limited pulse signal generationutilizing adiabatic soliton compression and optical time-divisionmultiplexing

0.8 ps TL pulses are successfully generated from a gain-switched DFB-LD by adiabatic soliton compression using a dispersion decreasing fiber (DDF). The compression ratio can be controlled using the peak input power into the DDF. We obtain a 10×2ⁿ Gb/s pulse stream by optically multiplexing the compressed pulses with a Mach-Zehnder (MZ) interferometer type multiplexer, in which n can be freely selected from 1 to 4 by controlling the coupling ratios of the couplers in the MZ interferometers. By using the demonstrated techniques, we can multiplex the initial pulse stream up to 160 Gb/s at the noninterfering duty factor of 0.2     

High average power, high repetition rate, picosecond pulsed fiber master oscillator power amplifier source seeded by a gain-switched laser diode at 1060 nm

We demonstrate a pulsed ytterbium-doped fiber master-oscillator power amplifier source at 1060 nm producing over 300 W of average power in 20-ps pulses at 1-GHz repetition rate. The pulses generated by a gain-switched diode were compressed by a chirped fiber Bragg grating and amplified without any distortion with excellent spectral quality. This fiber master oscillator power amplifier system offers versatility and potential for further power scaling.     

445 Mbit/s transmission field experiment at 1.55-µm wavelength region over 80 km using undersea optical-fiber cable

New transmission equipment employing a 1.55-μm distributed feedback laser diode (DFB-LD) to overcome fiber dispersion has been tested at environmental conditions using 1.3-μm zero-dispersion fiber cable on the undersea section of route F-400M. The DFB-LD's dynamic spectrum characteristics, in relation to power penalty, were examined and a suitable laser prebias control level was obtained. Field experimental transmission lines operated error free for a two-month period, and applicability to 1.55-μm 445-Mbit/s systems of over 100 km was shown.     

色散补偿法获得5GHz,6.8ps超短光脉冲

利用色散位移光纤压缩从１．５５μｍ增益调制ＤＦＢ激光器中出射的红移啁啾光脉冲。在最优光纤压缩长度下，光脉冲宽度由４２．６ｐｓ压缩至６．８ｐｓ，压缩比为６．３     

Full Characterization of Low-Power Picosecond Pulses From a Gain-Switched Diode Laser Using Electrooptic Modulation-Based Linear FROG

We use a linear frequency-resolved optical gating technique based on electrooptic modulation to fully characterize for the first time the highly chirped pulses from a 1.06-m Fabry-Perot laser diode and design a chirped fiber Bragg grating to provide high-quality pulse compression. With this grating, we achieved 18-ps pulses at a repetition rate of 1.35 GHz with a time-bandwidth product of 0.7.     

Generation of 20-fs optical pulses from a gain-switched laser diodeby a four-stage soliton compression technique

7.5-ps optical pulses generated from a gain-switched semiconductor laser at 2 GHz are successfully compressed down to 20 fs using a four-stage fiber soliton pulse compressor consisting of standard single-mode transmission, Er-doped, dispersion-decreasing, and dispersion-flattened fibers, respectively. We have experimentally confirmed that the soliton self-frequency shift plays an important role in obtaining such high compression in very short fibers, and also in minimizing the inherent undesirable pedestal component     

增益开关半导体激光器的三级脉冲整形方案

增益开关半导体激光器产生的光脉冲宽度往往较宽,且具有一定大小的脉冲基座。为了提高增益开关半导体激光器的脉冲质量,提出了一种三级脉冲整形方案。首先,利用色散补偿光纤将增益开关半导体激光器输出的光脉冲宽度从39.381 ps压缩到26.681 ps,随后利用掺铒光纤放大器和色散位移光纤的高阶孤子效应进一步将光脉冲的宽度压缩到20.916 ps,最后利用半导体光放大器的自相位调制效应区分开脉冲基座与脉冲中心的光谱,并利用光滤波器滤除脉冲基座对应的光谱部分,从而消减脉冲基座,并将脉冲宽度压缩到18.497 ps。实验结果表明,该三级脉冲整形方案可以有效地压缩脉冲宽度以及减小脉冲基座,从而提高增益开关半导体激光器输出光脉冲的质量。     

10-GHz 1.3-ps pulse generation using chirped soliton compression in a Raman gain medium

The authors demonstrate a novel pulse compression technique that is capable of producing high-quality 1.3-ps pulses at a repetition rate of 10 GHz. The technique begins with 20-ps pulses carved by a commercially available external modulator and achieves up to 15-fold compression using a combination of phase modulation and distributed Raman amplification. Unlike adiabatic soliton compression, the scheme takes advantage of an exact solution to the nonlinear Schrodinger equation for chirped soliton evolution. As such, high-quality low-pedestal compressed pulses can be produced in a shorter span of fiber than would be needed for adiabatic compression. Because the system uses external modulation, the source is inherently tunable. Furthermore, the degree of pulse compression can be adjusted by varying the amount of Raman gain and phase modulation.     

Transmission characteristics of a single-mode fiber in the 1.3-µm wavelength region

Transmission characteristics of 1.3-μm-band single-mode optical fibers were studied experimentally and theoretically. OH-ion content dependence of optical loss in the 1.3-μm region was investigated on single-mode fibers fabricated by the VAD method. The optical loss was evaluated for OH-ion content by calculating correlation factors between the optical loss and 1.39-μm OH-peak absorption loss. It was clarified that the optical loss calculated by correlation factors agreed approximately with the loss given by Lorentzian absorption in case of 0.0253-μm absorption half width, Next, the relationship between chromatic dispersion and fiber parameters was studied for step-index single-mode fibers. It was found that the zero-dispersion wavelength and the incline at the wavelength was expressed as simple functions of effective cutoff wavelength and relative index difference. Experimentally obtained zero-dispersion wavelengths on single-mode fibers fabricated by the VAD method were found to be in excellent agreement with the calculated values.     

System-Performance Analysis of Optimized Gain-Switched Pulse Source Employed in 40- and 80-Gb/s OTDM Systems

The development of ultrashort optical pulse sources, exhibiting excellent temporal and spectral profiles, will play a crucial role in the performance of future optical time division multiplexed (OTDM) systems. In this paper, we demonstrate the difference in performance in 40- and 80-Gb/s OTDM systems between optical pulse sources based on a gain-switched laser whose pulses are compressed by a nonlinearly and linearly chirped fiber Bragg grating. The results achieved show that nonlinear chirp in the wings of the pulse leads to temporal pedestals formed on either side of the pulse when using the linearly chirped grating, whereas with the nonlinearly chirped grating, pedestals are essentially eliminated. In an OTDM system, these pedestals cause coherent interaction between neighboring channels, resulting in intensity fluctuations that lead to a power penalty of 1.5 dB (40 Gb/s) and 3.5 dB (80 Gb/s) in comparison to the case where the nonlinearly chirped grating is used. Simulations carried out with the aid of Virtual Photonics Inc. verify the results achieved.