实用啁啾光纤光栅色散补偿器的研制

用相位掩模法制备了实用化的啁啾光纤光栅色散补偿器,补偿器的色散补偿量约为900ps/nm,3dB带宽约为0.6nm,峰值反射率约为99.9%,为了检验器件的性能,还在10Gbit/s的传输系统上做了补偿50km光纤的传输实验。     

Dispersion compensation of fiber Bragg gratings in 3100 km high speed optical fiber transmission system

By optimizing the fabrication process of the chirped optical fiber Bragg grating (CFBG), some key problems of CFBG are solved, such as fabrication repetition, temperature stability, group delay ripple (GDR), fluctuation of the reflection spectrum, polarization mode dispersion (PMD), interaction of cascaded CFBG, and so on. The CFBG we fabricated can attain a temperature coefficient less than 0.0005 nm/℃, and the smoothed GDR and the fluctuation of the reflection spectrum are smaller than 10ps and 0.5dB, respec-tively. The PMD of each CFBG is less than 1 ps and the dispersion of each grating is larger than -2600 ps/(nm·km). With dispersion compensated by the CFBGs we fabricated, a 13×10 Gbit/s 3100 km ultra long G.652 fiber transmission system is successfully imple-mented without electric regenerator. The bit error rate (BER) of the system is below 10-4 without forward error correction (FEC); when FEC is added, the BER is below 10-12. The power penalty of the carrier-suppressed return-to-zero (CSRZ) code transmission system is only 2.5 dB.     

Dispersion compensation based on sampled fiber Bragg gratings fabricated with reconstruction equivalent-chirp method

Using uniform phase mask and conventional fabrication technology with submicrometer rather than nanometer precision, a pure third-order dispersion-compensating fiber Bragg grating (DCFBG) and a tunable slope DCFBG are demonstrated with high performance based on the combined reconstruction equivalent-chirp method and an error correction technique. The former DCFBG has a dispersion varying from /spl sim/1000 to /spl sim/-1000 ps/nm in the 100-GHz passband and group delay ripple is less than /spl plusmn/5 ps. The latter has a dispersion slope varying from -150 to 150 ps/nm/sup 2/ within the 3-nm passband, and its group delay ripple is less than /spl plusmn/10 ps.     

Guided-wave optical equalizer with α-power chirped grating

A theoretical investigation of a guided-wave optical equalizer with an α-power chirped grating is presented. A group delay dispersion of 3700 ps/nm can be obtained at λ=1.55 μm by a chirped grating with α=0.3. It is shown that the chromatic dispersion of 200 km of a fiber whose zero-dispersion wavelength is located at 1.3 μm can be compensated at 1.55 μm to achieve up to 10 GHz signal bandwidth     

一种闭环控制的光纤光栅动态色散补偿仪

利用啁啾光纤光栅的应变调谐特性，将色散补偿的啁啾光纤光栅斜贴于悬臂梁的侧面，通过应力实现啁啾量调整而改变其色散补偿量的大小，同时利用固定在同一悬臂梁的均匀布拉格光栅传感器，实现了闭环自动控制色散补偿量，研制出了一种新型的光纤光栅动态色散补偿仪。该色散补偿仪工作在1550nm波段，典型性能数据为：色散动态补偿范围-1000-1680ps／nm，插入损耗小于1．5dB，动态调谐步进响应时间小于50ms，基本上能满足10Gb／s光纤通信系统中色散动态补偿的要求。     

宽带可调谐光纤光栅色散补偿器系统设计

文章提出一种在光纤光栅自身热膨胀效应产生啁啾的基础上,利用铝片热膨胀系数比较高的特点产生应力来增强光纤光栅啁啾,从而实现了宽带、大范围色散调谐的新型光纤光栅色散补偿器。该色散补偿器能够分别对群速度色散及中心波长独立调谐。实验结果表明,在中心波长为1 551.25nm处,能够实现>1.5nm的色散补偿带宽,-350～-690ps/nm的群时延色散调谐范围;在色散为-660ps/nm情况下,能够实现中心波长1nm的偏移。     

Grating compensation of third-order fiber dispersion

Subpicosecond optical pulses propagating in single-mode fibers are severely distorted by third-order dispersion even at the fiber's zero-dispersion wavelength (λ₀). Using cross-correlation techniques, the authors measured the broadening of a 100-fs pulse to more than 5 ps after passing through 400 m of fiber near λ₀. The measured asymmetric and oscillatory pulse shape is in agreement with calculations. A grating and telescope apparatus was configured to simultaneously equalize both third- and second-order dispersion for wavelengths slightly longer than λ ₀. Nearly complete compensation has been demonstrated for fiber lengths of 400 m and 3 km of dispersion-shifted fiber at wavelengths of 1560-1580 nm. For the longer fibers, fourth-order dispersion due to the grating becomes important     

Application of a Prechirp Technique to 10-Gb/s Transmission at 1064 nm Through 24 km of Photonic Crystal Fiber

The prechirp effect on 10-Gb/s transmission in the 1000-nm band over photonic crystal fiber (PCF) was investigated both experimentally and theoretically. We performed transmission experiments using a 24-km-long PCF whose optical loss and chromatic dispersion were 0.94 dB/km and$-$20 ps/nm/km at 1064 nm, respectively. We confirmed an improvement in the bit-error-rate performance after the transmission, namely a “negative power penalty” of about$-$0.5 dB. Our experimental result and theoretical estimation revealed that the signal degradation induced by the chromatic dispersion can be effectively suppressed by employing the prechirp technique with a conventional$Z$-cut lithium niobate modulator.     

Recompression of pulses broadened by transmission through 10 km ofnon-dispersion-shifted fiber at 1.55 μm using 40-mm-long opticalfiber Bragg gratings with tunable chirp and central wavelength

A 40-mm-long fiber Bragg grating with both tunable chirp and central wavelength is used to recompress pulses broadened by transmission through 10.0 km of non-dispersion-shifted fiber at 1.542 μm. 4.0-ps transform-limited pulses having an optical bandwidth of greater than 1 nm were broadened to 230 ps, and recompressed to 12 ps, showing compensation of 95% of the fiber dispersion     

保偏光纤偏振耦合系统的动态色散补偿

在白光保偏光纤(PMF)偏振耦合系统中,光纤双折射色散会引起干涉条纹包络随着光纤长度展宽,从而导致空间分辨率降低,光纤测量范围变小。为了减小双折射色散的影响,提出一种基于频域变换的色散相位补偿方法,通过干涉主极大包络与耦合点包络的宽度比求得相位补偿因子,并与非线性色散相位谱相乘,通过傅里叶逆变换得到色散补偿信号。实验分别对400m和1000m PMF进行了测试,得到光纤双折射色散系数为0.0116×10-9 ps/(nm.km),将测试系统对PMF 1000m处耦合点的空间分辨率由62.85cm提高到6.03cm,实现了对长距离PMF偏振耦合系统的动态色散补偿。     

A tunable four-channel fiber Bragg grating dispersion compensator

A tunable four-channel dispersion compensator is achieved using fiber Bragg grating technology and applying a temperature gradient along the grating. Any dispersion from -370 to -1420 ps/nm could be obtained.     

基于非线性啁啾光栅和波长扫描的ROF系统

为了降低光信号在不同传输距离产生的色散对光载射频(ROF)(光载无线电)传输系统的信号质量的影响,提出了一种基于静态非线性啁啾光纤光栅(NLCFBG)和动态波长扫描相结合的可调谐色散补偿ROF传输系统方案。在对所提出系统方案进行理论分析的基础上制作了NLCFBG,并对ROF传输中的可调谐色散效果进行半实物仿真,分析和比较了有无光栅色散补偿时系统的传输性能;验证了此方案对不同传输距离、不同激光频率以及不同射频载波频率的光纤传输系统色散补偿性能。     

2500 km-10 Gbps RZ transmission system based on dispersion compensation CFBGs without electric regenerator

The characteristics of chirped fiber Bragg gratings (CFBGs) are optimized so that the ripple coefficient of the power reflectivity spectrum and group time delay are less than 1 dB and |± 15| ps, group delay is about 2600 ps/nm, polarization module dispersion is very small, PMD<2 ps, -3 dB bandwidth is about 0.35 nm, and insertion loss is about 4-5 dBm. Using dispersion compensation CFBG, a 2500 km-10 Gbps RZ optical signal transmission system on G.652 fiber was successfully demonstrated without an electric regenerator by optimizing dispersion management and loss management. The RZ optical signal was generated through a two-stage modulation method. At 2081 km, the power penalty of transmission is about 3 dB (conditions: RZ signal, BER = 10-12, PRBS = 1023 - 1); At 2560 km, the power penalty is about 5 dB. It is superior to the system using NRZ under the same conditions.     

Cross-phase modulation in short-period dispersion managed fiber

Reports on the theoretical investigation of the cross-phase modulation (XPM) in a short-period dispersion managed fiber (SPDMF) system. The results show, that to minimize the XPM-induced intensity interference in an SPDMF, the dispersion of the negative section should be less than -14 ps/nm/km, assuming that the dispersion of the positive section was 17 ps/nm/km (as for a conventional single-mode fiber). Together with the design criteria for the suppression of four-wave mixing, this result could be used to optimize an SPDMF for use in high-speed wavelength-division multiplexing systems     

Tunable dispersion compensator based on a fiber Bragg grating written in a tapered fiber

We report a novel dispersion tunable device for first-order dispersion compensation. It is based on a fiber Bragg grating written in a tapered fiber with a specific profile. The taper profile allows tuning the dispersion of the grating by stretching the fiber while the linearity of the group delay is preserved. A device with 0.8 nm of useful bandwidth and dispersion value tunable over more than 400 ps/nm is reported.     

Waveform degradation due to dispersion effects in an optical CPFSKsystem

Waveform degradation due to polarization and chromatic dispersions in a single-mode fiber is calculated for a coherent CPFSK signal. For a single-mode fiber with polarization dispersion of ⩽1 ps, chromatic dispersion almost dominates the system. However, if a fiber has polarization dispersion of more than a few picoseconds and a chromatic dispersion of less than 0.1 ps/km/nm, which can be attained by using a dispersion-shifted fiber and/or by electric dispersion compensation, polarization dispersion will restrict transmission capacity. For instance, polarization dispersion of 5 ps will restrict a bit rate by ~60 Gb/s when chromatic dispersion is fully reduced using a dispersion-shifted fiber or applying electrical equalization     

Experimental evaluation of chromatic dispersion distortion inoptical CPFSK transmission systems

Receiver sensitivity degradations due to fiber chromatic dispersion without chromatic dispersion compensation in multigigabit optical continuous-phase frequency-shift-keying (CPFSK) transmission systems are evaluated experimentally and theoretically. Transmission distance limited by the chromatic dispersion of 15 ps/nm/km is estimated to be 130 km at 5 Gb/s and 33 km at 10 Gb/s     

利用光子晶体光纤实现10 Gb/s光传输系统的色散补偿

利用光子晶体光纤（PCF）在10Gb/s光传输系统中对普通单模光纤中传输的光脉冲进行了色散补偿，获得了很好的补偿效果。实验中，10Gb／s光脉冲序列经过2.163km普通单模光纤被展宽后．利用26m长光子晶体光纤对其进行色散补偿．补偿后脉冲基本恢复到了初始形状。进一步的理论计算表明，此光纤在C波段20nm波长范围内对普通单模光纤能够实现较好的色散斜率补偿，补偿后剩余色散小于5ps／nm。理论与实验结果表明光子晶体光纤在色散补偿方面具有很大的潜力．在未来光通信系统中将发挥重要作用。     

Highly accurate long-span chromatic dispersion measurement system by a new phase-shift technique

A highly accurate long span chromatic dispersion measurement system, which is based on a wavelength-division-multiplexing phase-shift technique and utilizes six laser diodes in1.2 sim 1.6 mum spectral region, has been developed. It is intrinsically free from error due to the fiber length variation caused by temperature changes under the measurement. The measurement accuracies of dispersion and Zero-dispersion wavelength are extremely good and within ±0.02 ps/km . nm and ±0.1 nm in 1250 ∼ 1450 nm spectral region in the case of a 10.5-km single-mode fiber measurement. The dynamic range is over 50 dB excluding system theS/Nmargin of 5 dB. Using this system, chromatic dispersion measurements of a 101.9-km pure-silica-core single-mode fiber and a 100.7 km concatenated dispersion-shifted single-mode fiber have been successfully carried out. The measured result has coincided with the arithmetical mean of those of constituent fibers.     

An chromatic dispersion monitoring method based on spectral-shift of SOA

A remnant dispersion monitoring method based on spectral-shift of SOA in high speed optical communication system with CSRZ format and single channel speed of 40 Gbit/s is proposed. The system performance can be optimized by careful choosing bandwidth and center wavelength of the optical fiber grating filter. The dynamical monitoring range is ±60 ps/nm and the monitoring precision is about 5 ps/nm. This method can be suitable for the application in dynamical dispersion compensation of high speed optical communication systems.