宽带色散补偿模块的开发

文章从理论出发设计了一种色散补偿光纤波导结构,并制备出一种高性能的色散补偿光纤.测试结果表明:该色散补偿光纤在1 525～1 625 nm波长范围内具有较大负色散,1 545 nm波长的色散系数为-141 ps/(nm·km).采用该色散补偿光纤成功制备出宽带色散补偿模块.G.652光纤传输链路经过该色散补偿模块的补偿后,C波段的残余色散小于5.0 ps/nm,C波段色散斜率也实现了100%的补偿.     

Design and optimization of photonic crystal fibers for broad-band dispersion compensation

Design of photonic crystal fibers (PCFs) for application of broad-band dispersion compensation is investigated by using an improved design model based on combination of a rigorous vector solver for modal properties and a scaling approach for dispersion characteristics. The newly designed PCF is shown to exhibit large normal dispersion up to -474.5 ps/nm/km, nearly five times of conventional dispersion compensating fibers, and compensate conventional single-mode fibers within /spl plusmn/0.05 ps/nm/km over a 236-nm wavelength range. Furthermore, the design model and methodology can be applied to design other dispersion-based devices such as dispersion flattened fibers and dispersion shifted fibers.     

1.6 Tbit/s transmission over 2160 km of field-deployed dispersion-managed fibre without per channel dispersion compensation

40/spl times/40 Gbit/s ultra-long haul transmission over 2160 km of cabled and field-deployed dispersion-managed fibre (DME) with extremely low total dispersion ripple (/spl plusmn/27 ps/nm over C-band) is demonstrated. No per channel dispersion compensation is required. A Q factor margin of 1.4 dB to standard 7% forward error correction limit is achieved.     

Novel fiber design for flat gain Raman amplification using single pump and dispersion compensation in S band

This paper reports on a novel fiber design that has an inherently flattened effective Raman gain spectrum. Simulations show that gain-flattened broad-band Raman amplification, using a single pump, can be achieved in any wavelength band by suitably choosing the fiber parameters and the pump wavelength. The fiber also has a high negative dispersion coefficient-(380-515) ps/km/spl middot/nm over the operating range of wavelengths-and the shape of the dispersion curve is such that the total link dispersion can be not only compensated but also flattened. Hence, the designed fiber can serve as a lossless, broad-band, dispersion-flattening, and dispersion-compensating module for the S band, wherein lossless operation is achieved using inherently gain-flattened single-pump Raman amplification. The performance characteristics of such a module was modeled taking into account wavelength-dependent splice loss as well as background loss, and it has been shown through simulations that lossless operation with /spl plusmn/0.2-dB gain ripple is achievable over (1480-1511) nm using a single pump. Moreover, dispersion compensation for five spans of transmission in a 10-Gb/s system, over this 32-nm bandwidth in the S band, should be attainable using the proposed design.     

Experimental demonstration of thin-film dispersion compensation for 50-GHz filters

Dispersion management is critical for next-generation high-bandwidth-utilization fiber-optical networks. Square-top thin-film bandpass filters for 50-GHz dense wavelength-division multiplexing inherently have high chromatic dispersion (CD) in transmission. The imparted dispersion power penalty on the network is undesirable. However, a second thin-film filter, operating in reflection, can be designed to compensate the CD of the bandpass filter. In this paper we demonstrate experimentally the reduction of the intrinsic CD of a 50-GHz thin-film coupler from /spl plusmn/170 ps/nm to /spl plusmn/50 ps/nm over a 30-GHz passband, through the use of such a cascaded thin-film compensator. Network simulations based on filter performance confirm the reduced dispersion power penalty of the cascade over the individual filter.     

Simulation and design for a tunable dispersion compensator package

A novel optical model for a tunable dispersion compensator is realized by a deliberate packaging scheme ensuing from intensive interactions of mechanical design, materials science and numerical simulation techniques including computational fluid dynamics and finite element analysis. The compensator is comprised of multiple cascaded single cavity Gires-Tournois etalons, each under independent temperature control. Three critical issues are addressed: etalon temperature uniformity, thermal insulation and optical surface deformation of the etalons. With etalon optical surface deformation minimized and etalon temperature uniformity successfully controlled within a range of /spl plusmn/0.1/spl deg/C, this small (232 /spl times/ 139 /spl times/ 16 mm) compensator achieves extremely low group delay ripple (<2.0 ps), low insertion loss ripple (<0.5 dB, insertion loss <6.3 dB), low polarization dependent loss [(PDL),<0.15 dB] and low polarization mode dispersion [(PMD),<0.7 ps]. The dispersion tuning range is from -700 ps/nm to +700 ps/nm in a dispersion passband of 0.2 nm which is sufficient for 10-Gb/s transmission. Thermal insulation design makes the tuning process take effect within 1 min at maximum power consumption 5 W.     

Low insertion loss and low dispersion penalty InGaAsP quantum-well high-speed electroabsorption modulator for 40-Gb/s very-short-reach, long-reach, and long-haul applications

We present a metal-organic-chemical-vapor-deposition-grown low-optical-insertion-loss InGaAsP/InP multiple-quantum-well electroabsorption modulator (EAM), suitable for both nonreturn-to-zero (NRZ) and return-to-zero (RZ) applications. The EAM exhibits a dynamic (RF) extinction ratio of 11.5 dB at 1550 nm for 3 Vp-p drive under 40-Gb/s modulation. The optical insertion loss of the modulator in the on-state is -5.2 dB at 1550 nm. In addition, the EAM also exhibits a 3-dB small-signal response (S21) of greater than 38 GHz, allowing it to be used in both 40-Gb/s NRZ and 10-Gb/s RZ applications. The dispersion penalty at 40 Gb/s is measured to be 1.2 dB over /spl plusmn/40 ps/nm of chromatic dispersion. Finally, we demonstrate 40-Gb/s transmission performance over 85 km and 700 km.     

A novel ultraflattened dispersion photonic Crystal fiber

A novel four-ring photonic crystal fiber (PCF) structure with two different air-hole sizes is proposed with nearly zero ultraflattened dispersion characteristics. Through optimizing only three geometrical parameters, two air-hole diameters, and one hole pitch, the ultraflattened zero dispersion PCF can be efficiently designed. As an example, a four-ring PCF with flattened dispersion of /spl plusmn/0.25 ps/km/nm from 1.295- to 1.725-/spl mu/m wavelength is numerically demonstrated. The corresponding design procedures for the novel PCF are also presented in this letter.     

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.     

1.6 Tbit/s(40×40 Gbit/s)光通信传输系统

在国家自然科学基金网(NSFCNet)上已实现由400 km×10 Gbit/s传输链路直接升级的一路400 km×40 Gbit/s光传输实验的基础上,采用自行研制的40×40 Gbit/s载波抑制归零(CS-RZ)码多波长光发送源,进行了160 km的1.6 Tbit/s(40×40 Gbit/s)波分复用(WDM)光传输实验。实验结果表明,对于常规中短距离10 Gbit/s传输链路可以直接升级至40 Gbit/s。但是由于40 Gbit/s传输系统的色散容限小于60 ps/nm,而且传输光纤与色散补偿模块的色散斜率不匹配,要实现40通道40 Gbit/s的传输,必须对40个信道分别进行精细的色散补偿。这也说明,对于宽带的40 Gbit/s多波长系统,有必要优化设计或更新传输链路。     

Impact of dispersion fluctuations on 40-Gb/s dispersion-managed lightwave systems

We study numerically the impact of random dispersion fluctuations on the performance of 40-Gb/s dispersion-managed lightwave systems designed using either the chirped return-to-zero or the soliton format and employing backward-pumped distributed Raman amplification. We consider two-section dispersion maps with /spl beta//sub 2/=/spl plusmn/4 and /spl plusmn/8 ps/sup 2//km and show that the Q parameter decreases rapidly in both cases as the nonlinear effects become stronger. The impact of dispersion fluctuations can be reduced by lowering the average input power, but the system length is then limited by amplifier noise.     

A novel design for dispersion compensating photonic crystal fiber Raman amplifier

This letter presents a novel design for dispersion compensating photonic crystal fiber (DCPCF) which shows inherently flattened high Raman gain of 19 dB (/spl plusmn/1.2-dB gain ripple) over 30-nm bandwidth. The proposed design module has been simulated through an efficient full-vectorial finite element method. The designed DCPCF has a high negative dispersion coefficient (-200 to -250 ps/nm/km) over C-band wavelength (1530-1568 nm). The proposed fiber module of 5.2-km length not only compensates the accumulated dispersion in conventional single-mode fiber (SMF-28) but also compensates for the dispersion slope. Hence, the designed DCPCF module acts as the gain-flattened Raman amplifier and dispersion compensator.     

Distributed dispersion measurements and control within continuously varying dispersion tapered fibers

We report the first continuous nondestructive measurement of dispersion along a fiber designed to have a continuously varying dispersion profile. This measurement highlights the flexibility of the measurement technique and illustrates the levels of accuracy [/spl ap/0.05 ps/(nm/spl middot/km)] that can be achieved when pulling long fibers with arbitrary dispersion profiles.     

Multimode fibers for compensating intermodal dispersion of graded-index multimode fibers

This paper proposes a novel type of multimode dispersion compensation fiber (MM-DCF) by which the intermodal dispersion of multimode fibers (MMFs) can be effectively compensated. A theoretical model that precisely calculates the group velocities of a target MMF and its MM-DCF and the power coupling between the two fibers is applied to confirm the proposal presented here. As a demonstration of the operation of the MM-DCF, an MMF optimized for transmission at a wavelength of 850 nm is compensated by the MM-DCF, and its overfilled launch bandwidth at a wavelength of 1300 nm is enhanced from 0.62 to 2.56GHz/spl middot/km.     

RZ-DPSK field trial over 13 100 km of installed non-slope-matched submarine fibers

This work presents the first field trial using the return-to-zero differential-phase-shift-keying (RZ-DPSK) modulation format. A 96/spl times/10-Gb/s RZ-DPSK field trial was conducted over a 13 100-km optical undersea path by double passing the installed 6550-km underwater link which was deployed with non-slope-matched submarine fibers. All channels performed with more than a 3-dB forward-error correction margin, including channels that accumulated over /spl plusmn/13 000ps/nm of dispersion. It is also shown that the RZ-DPSK format has similar residual dispersion and channel power tolerance for both slope-matched and non-slope-matched fibers. Furthermore, it is demonstrated that the chirped RZ-DPSK format could further improve system performance by 1-2 dB.     

PMD-induced transmission penalties in polarization-multiplexed transmission

In this paper, we investigate for the first time chromatic dispersion and nonlinearity tolerances in the presence of polarization-mode dispersion (PMD) for polarization-multiplexed (POLMUX) 2 /spl times/ 10-Gb/s nonreturn-to-zero (NRZ) transmission. In polarization-multiplexing, the interaction between fiber nonlinearity and PMD can lower the nonlinear tolerance beyond the tolerances evident when considering both transmission penalties separately; the combined penalties are significantly worse than in the case for non-POLMUX transmission. In this paper, we show, through simulations comparing POLMUX with non-POMUX transmission in the presence of nonlinearity, a reduction of about a factor of three in PMD tolerance. In addition, we show that the dispersion tolerance of POLMUX transmission is severely limited in the presence of PMD. For example, a 40-ps differential group delay (DGD) with worst case coupling of the polarization channels into the fiber lowers the dispersion tolerance, resulting in a 1-dB eye-opening penalty (EOP), from 1200 to 450 ps/nm. We conclude that the interaction between PMD, chromatic dispersion, and nonlinearity leads to the worst signal impairments in POLMUX transmission and increases the effort of using polarization-multiplexing as a modulation format.     

全光纤位移干涉测速系统中小波基的选取研究

为了使全光纤位移干涉测速系统能够准确稳定地测速,采用小波基分析问题的方法,对全光纤位移干涉测速仪信号进行了理论分析,并选取6种小波基函数进行计算机模拟,选定了适合全光纤位移干涉测速仪信号分析方法的最优小波基。与此同时,分别利用自由落体运动实验和高速爆轰实验验证了系统的精确性和稳定性,精确度达到99%,稳定性极高。结果表明,最优小波基的选取是合理的。     

NRZ-OOK-to-RZ-BPSK modulation-format conversion using SOA-MZI wavelength converter

A novel all-optical modulation-format conversion from nonreturn-to-zero on-off keying (NRZ-OOK) to return-to-zero binary phase-shift keying (RZ-BPSK) is proposed. A Mach-Zehnder interferometric (MZI) wavelength converter consisting of integrated semiconductor optical amplifiers (SOAs) is utilized to implement the proposed format conversion. Error-free operation at a bit rate of 10.7 Gb/s is experimentally demonstrated in order to show the feasibility of the proposed scheme. The received sensitivity of the converted signal is improved by 2.9 dB compared with a back-to-back NRZ-OOK signal at BER=10/sup -9/. In addition, a reasonable dispersion tolerance of the converted signal up to /spl plusmn/500 ps/nm is observed. The numerical simulation based upon the carrier-rate equation verifies the experimental results.     

Tunable dispersion compensation at 40-Gb/s using a multicavity etalon all-pass filter with NRZ, RZ, and CS-RZ modulation

We present a multichannel tunable dispersion compensator (TDC) based on multicavity all-pass etalons that is capable of operation at 40 Gb/s. The device has a tuning range of +200/-220 ps/nm with a group delay ripple < /spl plusmn/5 ps over a channel bandwidth of 80 GHz, an overall loss of < 5.2 dB, very low insertion loss ripple, and can operate on any channel on a 200-GHz grid over the C-band. In addition, we present system performance results at 40 Gb/s using NRZ, RZ, and CS-RZ modulation, compensating up to 45 km of nonzero dispersion shifted fiber (NZDSF). Our results show that this device introduces very little excess system penalty with signal frequency drifts of up to 20 GHz when operated near the center of its tuning range. For single channel experiments with fiber, the system penalty increase versus signal detuning is more significant, but can be reduced by dynamically optimizing the device dispersion during detuning. Finally, we demonstrate simultaneous compensation of 4 channels across the C-band over 25 km of NZDSF.     

Dispersion tolerance and transmission distance of a 40-Gb/sdispersion management soliton transmission system

We investigate the tolerance of the variation of average dispersion in a 40-Gb/s dispersion-managed soliton (DMS) transmission system. It is theoretically shown that dispersion tolerance is governed by pulse broadening and soliton interaction, and that the largest dispersion tolerance can be achieved by optimizing the pulse energy depending on the transmission distance. We construct a 40-Gb/s recirculating loop transmission system and show that the dispersion tolerance of over 180 ps/nm, which is much larger than that of a linear nonreturn-to-zero (NRZ) format system, can be realized by the optimization of the pulse energy at a transmission distance of more than 1000 km