Stability of two modes in DFB laser diode under high data rate modulation

Using a DFB-LD with two longitudinal modes in the 1.55 ?m region, the mode stability was examined experimentally. It is found that these modes are very stable under direct modulation at least up to around 300 Mbit/s and there is no power penalty due to mode partition noise in 97 km single-mode-fibre transmission at 280 Mbit/s.     

600 MHz direct modulation of short external cavity wavelength-tunable diode laser

The current modulation characteristics of a short external cavity tunable laser are presented. The 1540 nm Fabry-Perot diode laser is wavelength-tuned by the electrostatically controlled silicon micromachined Fabry-Perot interferometer device. The measured -3 dB cutoff frequency of 600 MHz is the widest reported direct modulation bandwidth of the external cavity tunable laser.     

Analysis of linewidth of separated-electrode DFB laser diode

Presents a new linewidth formula for DFB lasers, which includes the spatial hole burning effect. The linewidth of DFB lasers with three separated electrodes is calculated in various bias conditions. The optimum bias condition is discussed to obtain a narrow linewidth.<>     

DFB laser with attached external intensity modulator

A theoretical study is made of the frequency pulling effect exerted on a distributed feedback (DFB) laser by an external amplitude modulator that is directly attached to it. The modulator consists of a piece of waveguide whose loss is modulated by means of an externally applied voltage. The modulator affects the laser due to residual reflections from its far end which appear as a variable effective reflectivity to the output end of the DFB laser. Modulation affects the magnitude as well as the phase of the effective reflection coefficient presented to the laser due to the coupling of the real and imaginary parts of the effective refractive index of the modulator waveguide. The tuning problem is formulated as an eigenvalue equation for the DFB laser in the presence of an externally attached lossy cavity     

15-GHz modulation performance of integrated DFB laser diode EA modulator with identical multiple-quantum-well double-stack active layer

Monolithically integrated InGaAsP 1.55-/spl mu/m ridge waveguide distributed feedback laser diodes with an electroabsorption modulator using an identical active multiquantum-well (MQW) layer structure with two different QW types exhibit low-threshold currents <18 mA. The 3-dBe cutoff frequency of 200-/spl mu/m-long modulators exceeds 15 GHz. 10-Gb/s transmission experiments with a voltage swing of 1.0 V/sub pp/ demonstrate the potential of this novel integration scheme.     

1064-nm DFB laser diode modules applicable to seeder for pulse-on-demand fiber laser systems

Semiconductor DFB (Distributed feedback) laser diodes with an operating wavelength of 1064 nm, which is suitable for pulse-on-demand fiber laser, have been developed. The stable performance of CW and nanosecond/picosecond pulsed operation is reviewed. By applying gain-switching operation with a simple direct modulation technique, 50-ps pulse generation with a stable spectral single-mode property was obtained. For the efficient amplification of the obtained 50-ps pulse, a monolithic semiconductor optical amplifier (SOA) was integrated into the DFB lasers. An improved peak power of 300 mW at 50-ps pulse was observed with limited optical noise injection when the synchronous modulation technique of the DFB and the SOA was employed. Short cavity lasers showed a high-frequency response compared to the original DFB lasers and achieved a short pulse width of 13 ps by standard gain-switched operation.     

射频光传输雷达接收链路的系统优化

在雷达指标体系中,探测距离和目标分辨能力是其中的重要参数。而噪声系数（NF）和接收链路的压缩动态范围（CDR）则影响着这两个指标。随着射频光传输（ROF）在雷达接收链路中应用的推进,除了对光链路本身的探讨外,还需扩展到接收链路中微波和光波的协同分析。因此,将其中的微波前级放大、射频光传输（ROF）、微波后级放大进行耦合,普适性地探讨接收链路CDR和NF。例如,当光链路噪声功率谱密度为?164 dBm/Hz,光链路增益?20 dB时,可设计前级放大41 dB。在这种情况下,接收链路CDR_1dB达143 dB·Hz,噪声系数为4.15 dB,能够同时满足探测距离和目标分辨的要求。对外调制光链路而言,调制器的半波电压可选择在2.0~5.8 V之间,实现性能和成本的平衡。分析从系统角度出发,探讨了基于ROF的接收链路,能够满足雷达功能要求,同时,也为接收链路中电器件和光器件的设计提供了依据。     

Self modulation at gigahertz frequencies of a diode laser coupled to an external cavity

An external cavity coupled to a continuously operating GaAs diode laser has been found to cause modulation of the light output at a frequency within the range of 0.6?2.2GHz. The modulation depth is close to 100% and the linewidth is 200kHz.     

A tunable distributed amplification DFB laser diode (TDA-DFB-LD)

A novel wavelength-tunable distributed amplification distributed feedback laser diode (TDA-DFB-LD) is proposed and fabricated. The proposed structure provides synchronous change between the longitudinal mode and the Bragg wavelength in tuning; thereby continuous wavelength tuning can be realized with single control-current. Moreover, extended tuning is also possible with two control-currents. A continuous tuning range of 2.9 nm and an extended discrete tuning range of 15 nm are experimentally obtained with a 1.55-μm TDA-DFB-LD     

894nm外腔半导体激光器

介绍了一种基于Littrow结构的894 nm外腔半导体激光器的设计原理,给出了光栅转轴的优化点计算,分析了无跳模范围和实际转轴位置的关系,指出了实际光栅转轴点的合理位置.针对铯原子激光抽运磁力仪的应用要求,通过外腔的选频功能,以及低噪声激光电流源、低温漂温控器和低噪声压电陶瓷驱动器,实现了自由运转波长为904 nm的...     

Narrowband external cavity laser diode arra

A laser diode array line narrowing using an external cavity with a holographic grating is demonstrated. A linewidth of 11 GHz is obtained at an operating wavelength of 852 nm with an output power of about 10 W. Narrow linewidth high-power diode arrays can be used to pump alkali lasers and to produce spin polarised noble gases     

Realisation of flat FM response by directly modulating a phase tunable DFB laser diode

Flat and efficient FM responses in a wide frequency range were obtained by directly modulating the injection current of a 1.3 ?m phase-tunable DFB-DC-PBH laser diode. The FM response is flat between 1 kHz and 300 MHz, and the nor malised frequency deviation is 1?3 GHz/mA, which is 5?10 times larger than that of a conventional laser diode in the several hundred megahertz region.     

Intensity noise suppression and modulation characteristics of a laser diode coupled to an external cavity

Static and dynamic properties of a GaAlAs laser diode with an external cavity (1.5-50 cm) have been studied experimentally, it is found that the optical feedback induced intensity noise is strikingly suppressed by 30 dB when a single frequency oscillation is realized with good phase matching. The threshold of modulation depth, over which intensity noise increases abruptly, has been measured as a function of the modulation frequency in a range of 10-400 MHz. It has the maximum at about 40-70 MHz and increases with the decrease of the external cavity length. On the basis of the compound cavity model the phase and gain conditions for the single frequency oscillation are discussed and the threshold modulation depth is calculated, which is shown to be in good agreement with the experimental results.     

Oscillation frequency, linewidth reduction and frequency modulation characteristics for a diode laser with external grating feedback

Simple analytical expressions are given for the oscillation frequency, linewidth, FM noise spectrum and frequency modulation characteristics of a diode laser with external grating feedback. The analytical expressions are found to be in good agreement with experimental results and to be useful for quantitative predictions and optimisations of the external feedback controlled diode laser performance.     

All-optical actively modelocked fibre ring laser based on cross-gain modulation in SOA

A novel actively modelocked fibre ring laser based on cross-gain modulation in a semiconductor optical amplifier (SOA) employed as both the gain medium and modelocking element has been demonstrated. Stable uniform pulse trains with pulse-widths about 21 ps at 5 GHz repetition frequency were obtained. The entire laser was operated in the optical domain with a large tuning range that could probably span the whole gain region of the gain medium employed.     

Spectral characteristics of a DFB laser under high-speed direct modulation

Characteristics of a DFB laser under high-speed direct modulation are studied with an emphasis on the spectral analysis. A stable single-longitudinal-mode oscillation was confirmed up to 8.4 GHz direct modulation. The possibility of reducing the frequency chirping by device parameter optimisation is predicted on the basis of the experimental results obtained.     

Nonlinear distortions and compensations of DFB laser diode inAM-VSB lightwave CATV applications

The nonlinear distortions of a directly modulated laser diode applied to AM-VSB lightwave CATV systems are studied from the viewpoint of rate equations. A simple method for calculating composite second-order distortion (CSO) is proposed, which is called the quasidynamic approach. The contribution to nonlinearity from fiber dispersion and laser chirping is also discussed. The dependences on the variations of parameters of rate equations are investigated to determine the dominant factor for CSO degradation. This approach explains quite well the experimental results and suggests a method for constructing a predistortion circuit with at least 10 dB improvement     

Reduction of laser chirp in 1.5 ?m DFB lasers by modulation pulse shaping

The dynamic linewidth of 1.5 ?m ridge waveguide DFB lasers is shown to be reduced by shaping the pulse of the laser modulating waveform. Pulse shaping is performed by a second-order network designed to cancel the small-signal laser resonance. Results demonstrate a dynamic linewidth reduction from 1.4 ? to 0.55 ? FWHM for a 500 ps pulse.     

Characterization of the modulation and noise properties of athree-electrode DFB laser

The modulation and noise properties of a three-electrode DFB laser have been measured. At proper biasing, the frequency modulation response could be chosen to be in phase or 180° out of phase with respect to the intensity modulation by selecting the modulated electrode. Applying a first order equalization/filter, a flat frequency modulation response was measured up to 5 GHz. A 20-dB broadband suppression of the intensity modulation was accomplished when modulating two sections in push-pull. The spectral densities of the FM and intermodulation noise were measured showing remarkably flat intermodulation and FM noise spectra     

Wavelength conversion for frequency-modulated light using opticalmodulation to oscillation frequency of a DFB laser diode

A technique for wavelength conversion for frequency-modulated (FM) light is described. It utilizes the light-injection-induced frequency shift of a distributed-feedback (DFB) laser diode and the frequency-modulated-to-intensity-modulated (FM-IM) conversion function of the Mach-Zehnder (M-Z) optical filter. Input FM light is converted into IM light by the M-Z filter. The IM light is injected into the DFB-LD oscillating at another wavelength, modulating its oscillation frequency. The output from the DFB-LD has an FM signal identical to the input FM light. Thus, wavelength conversion for FM light is achieved. The characteristics of the frequency shift induced by this optical injection were experimentally studied using a λ/4 phase-shift DFB-LD. A wavelength conversion experiment was performed. In the experimental demonstration, FM light at 1.534 μm was converted into FM light at 1.550 μm