1.5 μm two-section Fabry-Perot wavelength tunable optical filter

A 1.5 μm two-section Fabry-Perot wavelength tunable optical filter is studied. As opposed to DFB filters, this wavelength tunable optical filter has the advantage that the wavelength tuning range and the transmission bandwidth can be designed independently. This two-section Fabry-Perot filter also controls the transmissivity (gain) and the transmission wavelength independently by current injection and the constant-gain and constant-bandwidth wavelength tuning is achieved. The wavelength tuning range is as wide as 188 GHz (15 Å), the constant-gain is as high as 23 dB and the constant-bandwidth is as narrow as 5 GHz during wavelength tuning. A 25-channel wavelength selection with less than -10 dB crosstalk is expected with this filter     

A tunable dual-wavelength erbium-doped fiber ring laser using a self-seeded Fabry-Perot laser diode

A tunable dual-wavelength erbium-doped fiber ring laser using a self-seeded Fabry-Perot laser diode (FP-LD) is proposed and demonstrated. By adding an FP-LD incorporated with a tunable bandpass filter within the ring cavity, the fiber laser can lase two wavelengths simultaneously because of the self-seeded mechanism. This dual-wavelength output exhibits a good performance having the optical side-mode suppression ratio over 31 dB. The wavelength-tuning range of this tunable dual-wavelength fiber laser can be up to 9 nm.     

Star-coupler-based optical cross-connect switch experiments withtunable receivers

An optical cross-connect switch using the star-coupler-based frequency-division-multiplex technique are discussed. Two specific tunable receivers have been implanted. The first is a heterodyne receiver with a tunable laser as the local oscillator (LO) and the second is a tunable filter followed by a direct-detection receiver. In the heterodyne receiver, the tunable LO was a monolithic three-section multiple-quantum-well distributed Bragg laser capable of a 1000-GHz tuning range. Receiver sensitivity was measured to be -38 dBm at 1 Gb/s (BER=10^-10). The power margin in the system substantiated feasibility for a 400×400 switch. In the tunable-filter receiver, the tunable filter is a tunable two-stage optical fiber Fabry-Perot filter design consisting of a narrowband filter followed by a wideband filter. The tuning of the filters is computer controlled, and the combined filter has a tuning range of 15000 GHz with a finesse of ≈5170. Therefore, it is capable of covering over 1000 channels of 2.9 GHz each     

Mutual pulse injection seeding by the use of two fabry-Perot laser diodes to produce wavelength-tunable optical short pulses

A mutual pulse injection-seeding scheme is developed to produce wavelength-tunable optical short pulses by the use of two Fabry-Perot laser diodes, of which one is gain-switched and the other is dc biased. Wavelength tuning of the optical pulses is achieved by simply adjusting a tunable optical filter while maintaining a constant repetition frequency of 3.0 GHz. The sidemode suppression ratio obtained is more than 30 dB over the wavelength-tuning range of 19 nm. The system is simple and robust.     

Continuously wavelength-tunable MQW fabry-perot laser diode pulse source with a fiber-based external cavity

A simple continuously wavelength-tunable fiber ring laser pulse source is demonstrated. Such a source employs a gain-switched multiple quantum-well Fabry-Perot laser diode in a self-seeding scheme and the output pulse wavelength can be tuned continuously via a tunable optical filter. The optical pulses generated exhibit a pulsewidth of 92 ps at the frequency of 2.6 GHz. Within a wide wavelength tuning range of 46 nm, the side-mode suppression ratio and the average power of the output optical pulses obtained are higher than 50.1 dB and 3.3 dBm, respectively, and the pulse spectral stability can be maintained in the whole wavelength tuning range.     

基于Hi-Bi FLM的离散式L带可调谐掺铒光纤激光器

研究了利用高双折射光纤环形镜（HiBiFLM）结合L带可调谐的波长选择薄膜滤波器,以掺Er^3＋光纤为增益介质,以0．8nm波长间隔计,可获得L波段41个离散可调谐波长的可调谐输出,各信道波长输出功率变化的最大幅度小于3．1dB,光信噪比（OSNR）优于32dB。     

互注入锁定产生波长可调谐光脉冲的实验研究

本文提出了一种利用两个F -P半导体激光器双向注入锁定产生波长可调谐光脉冲的实验系统。该实验系统只需调节可调谐滤波器就可以方便地选择不同波长的单纵模光脉冲,在2 5nm的波长调谐范围内边模抑制比(SMSR)为2 6dB ,其中18nm的波长范围内高于3 1dB。     

基于Fabry-Perot结构的可调波长选择光开关

本文提出波长选择光开关的概念,首次研制出一个基于Fabry-Perot结构的可调波长选择光开关,该开关为2×2光纤端口,每个端口携带N个波长,工作时可以选1个或多个波长,插入损耗小于3dB,波长调谐范围10nm,调谐机构为一对多层三明治结构的压电陶瓷,具有驱动电压低,小于5V的驱动电压可以达到3.3nm的调谐,最大开关时间为1毫秒,开关比优于30dB.最后还分析了其基本透射与反射光谱性能,并讨论其对光通信、光交换网络产生的重要应用价值.     

基于色散光纤环级联结构的可调谐带通微波光子滤波器

提出并验证了一种宽调谐带宽的带通微波光子滤波器设计方案。该滤波器借助可调谐光纤光栅Sagnac环对宽带光源进行均匀切割,产生波长间隔可调的连续光载波作为滤波器的抽头,结合色散光纤环级联结构,实现滤波器的可重构性。研究结果表明,在光电调制器和光电探测器的频率带宽足够大的情况下,当光纤光栅Sagnac环的臂长差在0.50~8.28mm内变化、可调谐光纤延迟线的最小变化步长为0.01mm时,该方案能够实现滤波器中心频率在8.0506~1333.2000GHz内调谐,调谐步长为161.01MHz,边瓣抑制比达到27dB。     

High-speed continuously tunable liquid crystal filter for WDMnetworks

We describe a high-speed wavelength tunable liquid crystal filter which can be utilized as the tuning element at the receiving end of wavelength division multiaccess (WDMA) optical networks. The filter uses chiral smectic A electroclinic liquid crystals as the active cavity material in a Fabry-Perot etalon in order to obtain a microsecond switching speed. Using the commercially available BDH764E liquid crystal material, we demonstrate a tunable optical filter both in a bulk Fabry-Perot and a fiber Fabry-Perot (FFP) configuration. A bandwidth of about 0.7 mm and effective finesse of 70 were obtained in the FFP configuration. A FFP tuning range of 13 nm with a switching time of less than 10 μs were measured at the operating wavelength of 1.55 μm. A theoretical analysis of the expected filter performance in the FFP configuration is given. Diffraction in the Fabry-Perot cavity is identified as the dominant loss factor, resulting in reduced throughput and finesse broadening. It is calculated theoretically that an effective finesse of 130 and a throughput loss of 2.2 dB are achievable for a mirror finesse of 200 and a liquid crystal cavity thickness of 5 μm. A short waveguide piece is assumed to be included in the cavity. Other expected loss sources for the filter in the FFP configuration have been calculated, showing negligible effect on the filter performance     

Tunable wavelength filtr in extrinsic fabry-perot of optical fiber

Characteristics of a tunable wavelength filter in extrinsic Fabry-Perot of optical fiber are studied both theoretically and experimentally in this paper. Using a slabby PZT-51, a tuning range of over 10nm is achieved by changing the distance between two fiber end faces. We chose a SLED to provide incident light into the filter and achieved a filter with narrow passband(subnanometer bandwidth). The basic characteristics of the filter, as well as the special properties of its output spectrum, are discussed and analyzed.     

Generation and distribution of a wide-band continuously tunable millimeter-wave signal with an optical external modulation technique

A new technique to generate and distribute a wide-band continuously tunable millimeter-wave signal using an optical external modulator and a wavelength-fixed optical notch filter is proposed. The optical intensity modulator is biased to suppress the odd-order optical sidebands. The wavelength-fixed optical notch filter is then used to filter out the optical carrier. Two second-order optical sidebands are obtained at the output of the notch filter. A millimeter-wave signal that has four times the frequency of the microwave drive signal is generated by beating the two second-order optical sidebands at a photodetector. Since no tunable optical filter is used, the system is easy to implement. A system using an LiNbO/sub 3/ intensity modulator and a fiber Bragg grating filter is built. A stable and high spectral purity millimeter-wave signal tunable from 32 to 50 GHz is obtained by tuning the microwave drive signal from 8 to 12.5 GHz. The integrity of the generated millimeter-wave signal is maintained after transmission over a 25-km standard single-mode fiber. Theoretical analysis on the harmonic suppression with different modulation depths and filter attenuations is also discussed.     

基于法布里-珀罗标准具的双环路光电振荡器

设计了一种基于法布里-珀罗(FP)标准具的双环路光电振荡器(OEO),该振荡器能将连续的光功率转换为稳定的频谱纯净的微波信号。FP标准具具有滤波的特性,因此可以替代普通OEO中的电滤波器从而降低电噪声,此外,FP标准具是一种高Q值的光学器件,可以缩短普通OEO所使用的光纤长度。双环路结构的引入能够更好地保证振荡器的单模输出,进一步降低相位噪声。仿真结果证明这种新型结构的OEO可以实现20GHz范围内振荡频率为15GHz的单模起振,边模抑制比超过150dB,使用的两条光纤环路长度分别为5m和36m。     

A dual-wavelength erbium-doped fiber laser with widely tunable wavelength spacing

A stable dual-wavelength erbium-doped fiber laser （EDFL） with tunable wavelength spacing and equalized output power is proposed and experimentally demonstrated. The fiber laser uses two fiber Fabry-Perot tunable filters （FFP- TFs） as the wavelength filter. The main cavity is divided into two sub-cavities with imbalance cavity losses through a 30/70 optical coupler. The tunable wavelength spacing can be achieved by changing the center wavelength of the filters and the equalized dual-wavelength output power can be achieved by properly controlling the variable optical attenuator （VOA） inserted in the lower-loss cavity.     

A novel fiber-optic Fabry-Perot resonator with two mode-conversionmirrors: proposal and application

A novel fiber-optic Fabry-Perot resonator composed of a piece of fiber with two LP₀₁&rlarr2;LP₀₂ mode-conversion reflectors is proposed and theoretically investigated. The reflective fiber-optic LP₀₁&rlarr2;LP₀₂ mode converter is analyzed based on the coupled-mode theory. The resonance characteristics including the transmission, reflection, and circulation of this novel fiber resonator are examined. In addition, we also describe the application of this device as an optical filter which can be used for FDM/WDM communications, etc. In contrast to a conventional Fabry-Perot optical filter with a periodic output spectrum, our proposed optical filter has only one peak in output spectrum, while the bandwidth of the filter spectrum is very narrow, with several Megahertz determined mainly by the cavity length of the fiber resonator. Finally, it is demonstrated that the characteristic of this optical frequency filter can be greatly improved by introducing a gain mechanism using a rare-earth-doped fiber. The tunable performances of this optical filter are also presented     

MEMS可调谐平顶窄带光学滤波器

设计了一种基于MEMS技术的可调谐光学滤波器,它通过光栅将输入的宽带光信号色散展开,以一个MEMS扭镜选择将对应滤波器通带的光信号反射至输出端,从而实现光学滤波和波长调谐功能。滤波器的输入端采用单模光纤,输出端采用多模或者少模光纤,可以实现窄带且平顶的通带特性。经过参数优化,仿真分析得结果显示,采用多模/少摸光纤输出的两种滤波器,其0.5 dB和25 dB带宽分别为0.95 nm/0.29 nm和1.39 nm/0.69 nm,分别满足100 GHz和50 GHz信道间隔的DWDM系统要求。由于输出端采用多模或者少摸光纤,从该滤波器输出的光信号不能继续在单模光纤中传输,只能由光探测器接收,因此该滤波器一般应用于全光网络节点中的下载端口。     

Tunable polymer double micro-ring filters

Based on the vernier effect, widely tunable polymer double micro-ring filters using the thermooptic effect or the electrooptic effect are demonstrated. A tuning enhancement factor of 40 was achieved at wavelengths near 1550 nm. The tuning rate for the thermooptic device is 120 GHz/mW and for the electrooptic device is 120 GHz/12 V. A tunable laser with a side-mode suppression ratio greater than 30 dB was demonstrated using this filter and erbium-doped fiber amplifier gain. Thermal tuning over 35 nm was achieved.     

A 100-channel optical FDM transmission/distribution at 622 Mb/sover 50 km

A 100-channel optical frequency-division multiplexing (FDM) transmission/distribution experiment at 622 Mb/s is demonstrated for a fiber length of 50 km. The feasibility of a polarization-insensitive waveguide frequency selection switch for 10-GHz intervals and a frequency-shift-keying (FSK) direct-detection scheme employing a Mach-Zehnder filter is verified. The demodulation circuit employs a Mach-Zehnder filter and a balanced receiver, which utilizes optical power more efficiently than the Fabry-Perot filter. No receiver sensitivity degradation is observed due to interchannel crosstalk of the 128-channel tunable waveguide frequency selection switch (FS-SW) or fiber four-wave mixing for transmissions over a 50-km-long nondispersion-shifted (NDS) fiber and a 26-km-long dispersion-shifted (DS) fiber     

Design and performance evaluation of narrowband rectangular optical filter based on stimulated Brillouin scattering in fiber

We propose a rectangular optical filter based on stimulated Brillouin scattering (SBS) in fiber with tunable bandwidth from 50 MHz to 4 GHz at 15-MHz tuning resolution. The steep-edged rectangular shape of the filter is precisely controlled utilizing digital feedback compensation of the multi-tone pump light. The passband ripple is \(\sim \)1 dB by nonlinearity management of the pump light and using the fiber with a single Brillouin peak. The filter selectivity is improved to more than 40 dB by using pump-splitting dual-stage configuration. We analyze the noise performance of the proposed SBS filter and demonstrate a sub-band extraction of a multi-band orthogonal frequency division multiplexing (OFDM) signal. Furthermore, we validate the amplification performance with different gains for OFDM signal, which shows the potential capability of the filter in the fields of optical signal processing.     

Quasicontinuous tunable fiber-ring laser applied as localoscillator in an absolute calibrated spectrometer for WDM systems

A special tunable fiber-ring laser is introduced. With this laser as local oscillator, a calibrated optical spectrometer was realized, which allows the determination of the wavelength of all transmitters of a wavelet division multiplexing (WDM) system in one sweep. The system is based on a fiber ring laser including a high finesse Fabry-Perot resonator with a high free spectral range and a 1-km-long dispersion shifted fiber. To achieve a high wavelength determination accuracy two auxiliary signals are generated: one with a Krypton filled absorption tube and another with a simple, silica based, periodical filter. With that, the wavelength of every transmitter of a WDM signal can be determined with an absolute frequency accuracy of better than ±0.8 GHz in a range of 1527-1562 nm in one sweep. The relative frequency accuracy is better than ±0.3 GHz