Integrated optical, acoustically tunable wavelength filter

A TM/TE convertor is combined with a TE-pass polariser on a common LiNbO/sub 3/ chip to obtain an integrated optical, acoustically tunable wavelength filter. Its tuning range is 1.45-1.57 mu m wavelength with a filter half-width of 2.8 nm. Due to the combined acoustical/optical strip guide structure used in the mode convertor, a very low acoustic drive power of only 9 mW is required.<>     

基于电吸收调制器的非相干可调谐微波光子滤波器

提出一种新的基于电吸收调制器(EAM)的非相干可调谐光子滤波器。首先通过带通滤波器滤除EAM输出的一个边带,获得单边带调制;再通过调谐EAM的偏置端,使得边带所引入的相移随着偏置电压的改变而改变,这样就可以实现一个真相移(TPS)结构;然后引入另一个非相干光源和Mach-Zender调制器(MZM),利用两路信号的延时不同实现一个基本的滤波器;最后通过调谐偏置所引入的TPS实现滤波器的宽带可调谐,而滤波器的形状可以保持不变,其中滤波器的调谐范围由偏置所引入相移的变化范围来决定。     

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.     

Variable bandwidth and tunable centre frequency filter usingtransversal-form programmable optical filter

The authors report the realisation of an integrated-optic variable bandwidth and tunable centre frequency filter using a transversal-form programmable optical filter with 32 taps. The bandwidth is varied from 44 to 84 GHz with a fixed centre frequency. Also, the centre frequency is tuned over 105 GHz with a fixed bandwidth     

A band-pass microwave photonic filter based on Lyot-Sagnac filter and cascaded optical structures

A band-pass microwave photonic filter（MPF）based on Lyot-Sagnac filter and two cascaded optical structures is demonstrated.In the experiment,a stabilized and tunable multi-wavelength optical source is obtained by slicing the broadband optical source（BOS）with a Lyot-Sagnac filter.A standard single-mode fiber（SMF）and a fiber ring resonator are cascaded to improve the mainlobe-to-sidelobe suppression ratio（MSSR）and Q-factor of the filter.The analysis shows that MSSR and Q-factor are improved by reducing the split ratio of the coupler or increasing the length of fiber in fiber ring resonator.The results have significant guidance for MPF design by choosing appropriate devices and parameters.Based on the analyses,a band-pass filter with MSSR of 53.54 dB and Q-factor of 4048 is achieved by choosing the split ratio of0.01,the length of SMF of 30 km and the length of fiber in fiber ring resonator of 152.27 cm.     

Tunable wavelength spacing multi-wavelength ring laser using programmable DGD module as intra-cavity filter

A multi-wavelength fibre laser whose channel spacing can be dynamically and continuously tuned is demonstrated experimentally. A novel programmable magneto-optic-based DGD module is used as the intra-cavity optical filter to control the wavelength spacing. Channel spacing tunable from 0.4 to 1.6 nm is achieved.     

A continuously tunable microwave photonic notch filter with complex coefficient based on phase modulation

A continuously tunable microwave photonic notch filter with complex coefficient based on phase modulation is proposed and demonstrated. The complex coefficient is generated using a Fourier-domain optical processor (FD-OP) to control the amplitude and phase of the optical carrier and radio-frequency (RF) phase modulation sidebands. By controlling the FD-OP, the frequency response of the filter can be tuned in the full free spectral range (FSR) without changing the shape and the FSR of the frequency response. The results show that the center frequency of the notch filter can be continuously tuned from 17.582 GHz to 29.311 GHz with FSR of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.     

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 widely tunable microwave photonic notch filter with adjustable bandwidth based on multi-wavelength fiber laser

A widely tunable microwave photonic notch filter with adjustable bandwidth based on multi-wavelength fiber laser is proposed and demonstrated. The multi-wavelength fiber laser generates the multi-taps of the microwave photonic filter (MPF). In order to obtain notch frequency response, a Fourier-domain optical processor (FD-OP) is introduced to control the amplitude and phase of the optical carrier and phase modulation sidebands. By adjusting the polarization controller (PC), different numbers of taps are got, such as 6, 8, 10 and 12. And the wavelength spacing of the multi-wavelength laser is 0.4 nm. The bandwidth of the notch filter is changed by adjusting the number of taps and the corresponding bandwidths are 4.41 GHz, 3.30 GHz, 2.64 GHz and 2.19 GHz, respectively. With the additional phase shift introduced by FD-OP, the notch position is continuously tuned in the whole free spectral range (FSR) of 27.94 GHz. The center frequency of the notch filter can be continuously tuned from 13.97 GHz to 41.91 GHz. This work has been supported by the National Natural Science Foundation of China (No.11444001), and the Municipal Natural Science Foundation of Tianjin in China (No.14JCYBJC16500). E-mail:cynever@163.com      

Frequency and wavelength tunable optical microwave source based on a distributed Bragg reflector self-pulsation laser

A frequency and wavelength tunable self-pulsation laser based on DBR laser devices is reported for the first time.This laser generates continuous tunable optical microwave in the range of 1.87-21.81 GHz with 3-dB linewidth about 10 MHz by tuning the injection currents on the front and back gain sections,and exhibits wavelength tuning range from 1536.28 to 1538.73 nm by tuning the injection currents on the grating section.     

基于DBR结构自脉动激光器的波长及频率可变光微波源

首次报道了基于DBR结构自脉动激光器的波长及频率可变光微波源。该微波源可以或得1.87GHz至21.81GHz的微波信号同时可以获得1536.28nm至1538.73nm的波长调谐。     

Instantaneous microwave frequency measurement based on hybrid microwave photonic filter

A novel photonic technique for instantaneous microwave frequency measurement based on hybrid microwave photonic filter （HMPF） is proposed and experimentally demonstrated. The HMPF is composed of an all-pass filter and a band-pass filter with negative coefficients. By properly controlling the power relationship between the all-pass filter and the band-pass filter, the HMPF can realize a monotonic frequency response, and then a unique relationship be- tween the output power and the input frequency is established. A high measurement resolution can be achieved for a given frequency range.     

基于啁啾相移FBG的宽调谐单通带微波光子滤波器

为扩大单通带微波光子滤波器(MPF)的可调谐 范围,提出了一种基于啁啾相移光纤光栅(PS-FBG) 的宽调谐单通带MPF。首先对普通PS-FBG的反射谱和基于普通PS-FBG的单通带MPF频率响应 进行了理 论和实验研究;然后,采用传输矩阵方法分析了啁啾PS-FBG的相移量、折射率调制深度以 及相移点位置 对其反射谱特性的影响,进而分析了对基于啁啾PS-FBG的单通带MPF频率响应的影响。结果 表明,调节可调谐激光 源的波长,可实现单通带频率的可调;相对于普通PS-FBG,啁啾PS-FBG扩大了反射谱带宽 ,从而单通带MPF扩大了可调谐范围。适当设计啁啾PS-FBG的相移点的位置,可以使单通带M PF的可调谐范围进一步增加。     

A tunable microwave photonic filter with complex coefficient based on slicing spectrum and stimulated Brillouin scattering

In this paper,we propose a method to realize microwave photonic filter(MPF) with complex coefficient,whose central frequency f 0 and 3 dB bandwidth are tunable.The complex coefficient is realized by multi-wavelength optical source and stimulated Brillouin scattering(SBS).The central frequency of the filter is tuned by adjusting the phase shift caused by SBS without changing its frequency response.The frequency selectivity of filter can be improved through increasing the bandwidth of broadband optical source(BOS) or decreasing wavelength separation to increase the taps of MPF.The mainlobeto-sidelobe suppression ratio(MSSR) of the filter is affected by the weight of each tap.When the length of fiber is 0.5544 m in birefringence fiber loop mirror(FLM),the MSSR is improved by 18.55 dB compared with that without the weight controlling.     

基于双光源的可调谐微波光子滤波器

提出了一种基于双光源与双相移光纤光栅(DPS- FBG)的可调谐微波光子滤波器。双光源经过相 位调制后,利用DPS-FBG的反射模式中的两超窄陷波分别对两相位调制光信号的边带进行抑 制,实现相 位调制至强度调制的转换。通过调节两光源的中心波长可以实现单通带与双通带之间的切换 ,实现单通带 的中心频率可调以及3dB带宽可调,实现双通带频率同时可调或者单独可调。建立了理论模 型并进行了数 值分析,最后通过实验进行了验证。实现了滤波器通带的3dB带宽由180MHz增加为319MHz,中心频率从1GHz到7GHz可调。     

Continuously tunable photonic microwave true-time delay based on tunable chirped fibre Bragg grating

A simple scheme for the photonic microwave true-time delay with high tunability based on a tunable chirped fibre Bragg grating without centre wavelength shift is experimentally demonstrated. A large dynamic range of true-time delay from 20 to 200 ps was achieved for a microwave signal carried over an optical signal.     

An adaptive wavelength tunable optical filter employing anangle-tuned interference filter and an intelligent digital controller

This paper describes an adaptive wavelength tunable optical filter, which is composed of an angle-tuned interference optical filter and an intelligent digital controller. The new angle-tuned interference filter consists of a dielectric interference optical filter and a piezoelectric angle-tuning mechanism. It achieves quick wavelength switching within 2.5 ms in a 30 nm tuning range and a sufficiently low crosstalk less than -30 dB. The intelligent digital controller has two functions: wavelength tracking and wavelength channel selection. Combining these technologies, we have developed a practical low-cost tunable filter suitable for a post-optical-amplifier filter in a high-sensitivity detection system and a channel selector in a WDM system that requires 10-100 ms channel selection time. With a wavelength tracking operation, we have confirmed -35 dBm high-sensitivity detection in 20 nm wavelength range in a 10 Gb/s system. We have also confirmed a wavelength channel selection operation within 18 ms in a three-channel wavelength division multiplexed (WDM) system whose channel spacing is 4.4 nm     

A cascaded microwave photonic filter based on a low-coherence infinite-impulse-response filter

A cascaded filter combining active and passive filters is proposed. The active filter acts as a low-coherence infinite-impulse-response (IIR) filter and achieves a sharp frequency response. The low-coherence IIR filter is realized by employing the cross-gain modulation (XGM) of the amplified spontaneous emission (ASE) spectrum of the semiconductor optical amplifier (SOA). The passive filter is an n-section unbalance Mach-Zehnder (UMZ) structure, which is used to increase free spectral range (FSR) and Q factor further. The low-coherence IIR filter cascaded with one section of UMZ passive filter is experimentally demonstrated, and a Q factor of 1268 is obtained.     

Electronic wavelength tuning using acoustooptic tunable filter with broad continuous tuning range and narrow channel spacing

The use of acoustooptic tunable filters as tunable-wavelength filters in a multiwavelength network is reported. Fast ( approximately=3 mu s access time), broad, continuous tuning (1.3-1.56 mu m) and narrow channel spacing (4.5 nm) in a nine-channel distribution system were demonstrated. The combination of broad tuning range and narrow channel spacing allows channel selection in a distribution system with hundreds of wide-band wavelength-division-multiplexed channels. The wavelength switching time, measured as approximately=3 mu s, is important in many high-speed switching applications.<>