30 Gbit/s downstream capacity of cost-effective colourless WDM-PON based on injection-locked Fabry-Perot lasers

A 100 GHz spaced comb, generated by a quantum dash passively modelocked laser, is used as a low-noise coherent seeding source for the colourless wavelength-division-multiplexed passive optical network based on injection-locked Fabry-Pe rot laser diodes. Error-free downstream transmission over 25 km singlemode fibre of 12 WDM channels at 2.5 Gbit/s with 100 GHz channel spacing is experimentally demonstrated.     

基于FP-LD实现副载波信号产生

采用一种基于法布里-珀罗腔激光二极管(FP-LD)的副载波信号的产生方案,此方案主要包括一个FP-LD和一个电光相位调制器(PM)。首先利用可调谐激光器、电光PM及微波源产生光正弦相位调制信号,将该信号注入到FP-LD中,通过FP-LD的注入锁定将该信号转换为副载波信号。在实验中,分别以2、3、4和5 GHz的调制频率注入到FP-LD中,相应得到22、21、24和25 GHz的副载波信号。     

Generation of ultrahigh-speed tunable-rate optical pulses usingstrongly gain-coupled dual-wavelength DFB laser diodes

A novel and simple method to generate a variable-rate, ultrahigh-speed optical pulse train is demonstrated using a dual-wavelength, strongly gain-coupled distributed-feedback laser diode. The repetition rate of the optical pulse train is continuously tunable from 25 to 80 GHz and no high-speed electronics are required in this method     

11.2 GHz picosecond optical pulse generation in gain-switched short-cavity InGaAsP injection lasers by high-frequency direct modulation

We report the generation of high-speed optical pulses in gain-switched short-cavity InGaAsP injection lasers by high-frequency direct modulation. Short pulses (25 ps) with high on/off ratio were obtained at 11.2 GHz from a short-cavity double-channel planar buried-heterostructure (DCPBH) InGaAsP semiconductor laser biased at three times the threshold current. This is the first report of direct modulation above 10 GHz for InGaAsP lasers.     

Impact of laser linewidth on optical channel spacing requirements for multichannel FSK and ASK systems

The sensitivity penalty is evaluated for amplitude-shift-keyed and frequency-shift-keyed multichannel coherent systems that use lasers with linewidths which are a significant fraction of the bit rate. The study was conducted for both ASK and FSK systems using a single-filter receiver with nonsynchronous detection. For FSK systems, both NRZ (nonreturn-to-zero) and alternate mark inversion (AMI) signal formats were studied. The optical channel spacing is strongly determined by the laser linewidth. For example, with the FSK-NRZ data rate of 150 Mb/s, the optical channel spacing which gives 1-dB crosstalk penalty is 4 GHz when the intermediate frequency linewidth is 50 MHz (laser linewidth is 25 MHz), as opposed to 1.8 GHz when the linewidth is negligible.<>     

High-Power Picosecond Pulse Generation Due to Mode-Locking With a Monolithic 10-mm-Long Four-Section DBR Laser at 920 nm

A 10-mm-long four-section distributed Bragg reflector laser with a double-quantum-well heterostructure at 920 nm was realized. A maximum optical pulse power of 3.6 W with a repetition rate of 4.1 GHz corresponding to the laser length was reached. The full-width at half-maximum of the pulses was 7 ps measured with an autocorrelator. A maximum pulse energy of 25 pJ was reached.     

High-speed and low-driving-voltage X-cut LiNbO3 opticalmodulator with two step backside slot

A newly designed low-driving-voltage X-cut lithium niobate optical modulator with a two step backside slot is proposed. This modulator was fabricated with micro-machining technology utilising excimer laser ablation. The modulation bandwidth of this modulator achieves 25 GHz and the driving voltage is 2.8 V at 1 kHz     

Microwave modulation of a quantum-well laser with and withoutexternal optical injection

We compare three microwave modulation methods experimentally and theoretically using a semiconductor quantum-well (QW) Fabry-Perot test laser: (1) direct microwave current modulation of the test laser (electrical modulation); (2) optical modulation by an external single-wavelength pump laser with a modulated optical injection power; and (3) electrical modulation of the test laser that is injection locked by an external single-wavelength pump laser with a constant injection power. This is the first direct comparison of the three modulation methods on the same QW laser, to the best of our knowledge. The bandwidth of optical absorption modulation is 7.7 GHz, which is 1.45 times the direct electrical modulation bandwidth (5.3 GHz) at a bias current of 30 mA in the test laser. On the other hand, the electrical modulation of the test laser under injection-locking condition has a significantly higher modulation bandwidth (10.5 GHz) than both the electrical and optical modulation methods     

Synchronized harmonic frequency mode-locking with laser diodes through optical pulse train injection

An ultrahigh-frequency optical pulse train from a monolithic mode-locked laser diode was stabilized by a novel method. When a stabilized optical pulse train was injected into a passively mode-locked laser diode whose repetition frequency was an integer multiple of the injected one, the output optical pulse train was harmonically synchronized and highly stabilized. This kind of operation was observed up to 40 GHz with 1 GHz optical pulse injection.     

80-160-GHz mode-locked fiber ring laser synchronized to external optical pulse stream

The authors present a novel scheme to generate ultrahigh repetition rate picosecond pulses synchronized to an optical pulse stream in an actively mode-locked fiber ring laser. A monolithic Mach-Zehnder interferometer with integrated semiconductor optical amplifiers serves as an 80-GHz optically controlled modulator. 80-GHz transform-limited 2.1-ps Gaussian pulse with low timing jitter, extinction ratios up to 25 dB, and 5 mW of average output power are demonstrated. The laser is wavelength tunable over more than 15 nm around 1555 nm. At 160 GHz, 2.5-ps pulse trains with 3-mW output power are generated by rational harmonic mode locking.     

Optical sweeper with double-heterodyne frequency-locked loop

An optical sweeper is constructed with a 1.5 mu m distributed Bragg reflector (DBR) laser for quick frequency-response measurement of high-speed optical receivers. The laser is successfully controlled over a 16 GHz tuning-range by using a double-heterodyne frequency-locked loop. S/N-improved measurement is also demonstrated at sweep speeds as fast as 1 GHz/s.<>     

A Multiwavelength Low-Power Wavelength-Locked Slotted Fabry–Pérot Laser Source for WDM Applications

Wavelength-locking of a multiwavelength stabilized slotted Fabry-Peacuterot (SFP) laser to a single-mode laser source is experimentally demonstrated. The SFP resonates at channels spaced by ~8 nm between 1510 and 1565 nm over a wide range of temperatures and drive currents. Under low-power (<-20 dBm) external optical injection, wavelength-locking with a sidemode suppression ratio (SMSR) >25 dB is achieved. A locking width of >25 GHz and SMSR >30 dB can be achieved for each locked wavelength channel at injection power >-16 dBm     

Optical narrow-band filters using optical amplification withdistributed feedback

The amplification characteristics of the distributed-feedback (DFB) laser amplifier are studied. The amplifier has a narrow, single-frequency gain-bandwidth product and the maximum-gain frequency tunability. With these advantages, the amplifier can be applied as an optical narrowband filter. This filter has optical frequency selectivity with an extinction ratio of better than -15 dB for optical inputs separated by 9.8 GHz having different optical input powers. By using a multielectrode DFB laser amplifier, the wide-range tunability of a gain maximum frequency (33.3 GHz) can be obtained while maintaining a constant gain and a constant gain-bandwidth product. Optical frequency selection with an extinction ratio of better then -20 dB can be obtained for two optical inputs separated by 15.4 GHz and having the same input power     

Dynamical behavior of a semiconductor laser with filtered externaloptical feedback

We report on a theoretical analysis of the dynamical performance of a semiconductor laser under the influence of delayed weak filtered external optical feedback. The filter widths considered range from 1 to 100 GHz. The analysis concentrates on the well known low-frequency fluctuations (LFFs) regime, in which LFFs occur in the absence of filtering. As expected, filtering the feedback light stabilizes the system in general. LFF can already be suppressed for moderately broad filters (25-50 GHz). In that case, the system was found to operate on the maximum gain mode with a small amplitude limit cycle. We show how the filtering can, in principle, be used for targeting the laser on the maximum gain mode     

Passively modelocked 50 GHz Er:Yb:glass laser

A diode-pumped Er:Yb:glass miniature laser has been passively mode locked to generate 2.0 ps pulses at a 50 GHz repetition rate with up to 7.5 mW average power. By combining this laser with a dynamic gain equaliser, a flat optical spectrum has been generated with up to 10 discrete channels with a 50 GHz channel spacing locked to the 50 GHz ITU grid.     

Experimental demonstration of a diode laser-excited optical filterin atomic Rb vapor

A narrow-bandwidth optical filter using diode-laser-pumped atomic Rb vapor has been demonstrated. Excellent rejection of off-resonant laser photons has been achieved. The measured detection bandwidth was 1.18 GHz at the Rb cell temperature of 150°C, which shows a good agreement with the calculated detection bandwidth of 1.02 GHz. The quantum efficiency of the atomic Rb vapor laser-excited optical filter is linearly dependent on the diode laser pumping power     

基于分布反馈注入锁定的连续可调光子微波倍频实验研究

提出了一种基于注入锁定分布反馈式(DFB)激光器的双波长差频微波/毫米波信号产生方案。方案利用正弦波光信号通过半导体光放大器(SOA)进行非线性展宽,产生高阶分量,然后注入到两个DFB激光器后进行锁定放大,产生频率连续可调的倍频信号。在实验中,注入的正弦波光信号频率为1.25GHz,得到20～40GHz频率范围内1.25GHz的任意自然数倍的连续可调微波信号,其最高倍频数为32。     

全光高速同步时钟信号的产生

采用 2 5GHz光脉冲序列作为低速时钟 ,将其注入一含半导体光放大器 (SOA)的锁模光纤激光器中 ,利用SOA的交叉增益调制效应 ,采用有理数谐波锁模技术 ,产生了 2～ 7倍同步群路时钟信号。利用这一技术可以为未来高速光时分复用 (OTDM)通信网络中心处理单元提供同步控制时钟。     

Dual-band bandpass tunable microwave photonic filter based on stimulated Brillouin scattering

A dual-band bandpass microwave photonic filter(MPF) based on stimulated Brillouin scattering(SBS) is theoretically analyzed and experimentally demonstrated. Two separated tunable laser sources(TLSs) are employed to generate two passbands by implementing phase modulation to amplitude modulation conversion by using SBS induced sideband amplification. The center frequencies of both passbands can be independently tuned ranging from 1 GHz to 19 GHz. High resolution with 3 d B bandwidth less than 30 MHz and large out-of-band rejection about 40 d B under 25 m W optical pump power are achieved.     

High-repetition-rate optical pulse generation using a rationalharmonic mode-locked fiber laser

Rational harmonic mode locking takes place in an actively mode-locked fiber laser when the modulation frequency f_m=(n+1/p)f_c, where n and p are both integers and f_c is the inverse of the cavity round-trip time, the 22nd order of rational harmonic mode locking has been observed when f_m ≈1 GHz. An optical pulse train with a repetition rate of 40 GHz has been obtained using a modulation frequency f_m=10 GHz. The theory of rational harmonic mode locking has also been developed. The stability of the mode-locked pulses is improved considerably when a semiconductor optical amplifier is incorporated into the fiber laser cavity. The supermode noise in the RF spectrum of a mode-locked laser is removed for a certain range of current in the semiconductor optical amplifier