Research On The Technology Of All-Optical Wavelength Conversion Of OFDM Signals

As one of the key technologies in future wavelength divssion multiplexing(WDM)all optical network(AON),all-optical wavelength conversion(AOWC)technology can avoid the limits of electronic bottlenecks,effectively resolve contention of the channel wavelength of the network,implement wavelength routing,reduce the channel wavelength blocking of the network,dramatically increase network throughput,and,in general,make a better use of the network resources under dynamic traffic patterns.The performance of wavelength converter is directly related to the performance of AON,accordingly,the research on the technology of AOWC has been paid great attention,it has become a hotspot.Orthogonal frequency division multiplexing(OFDM)technology,which has the advantages of high-spectral efficiency,robust fiber channel dispersion tolerance,large transmission capacity,adaptive modulation strategy,and strong anti-interference,has been widely employed in optical fiber communications.Unlike conventional digital signals in single-carrier modulations,optical OFDM waveforms in the time domain are analogue and fluctuate like random noise.This unique feature demands the linear conversion to all-optical wavelength converters in order to avoid distortions of the wave form.However,at present,there are few studies on the AOWC of OFDM signal.In this paper,it is elaborated the present researches of the AOWC of OFDM signal.A new scheme of the AOWC of OFDM signal is proposed by using two-mode injection locking(TMIL)in a Fabry–Pérot(FP)laser for the first time.The control signal and the probe signal at a milliwatt power level are combined and injected into the FP laser.By a proper control,they can be injection-locked to two longitudinal modes in the FP laser and subsequently,the transmission of the probe signal is conditioned by the control signal(that it is,to realize the AOWC).The AOWC of OFDM signal based on this scheme is numerically and experimentally researched,the specific work is as follows:Firstly,it was built the simulation platform of AOWC of OFDM signal based on TMIL in a FP laser,verified the validity of the scheme.The performance and stability of the proposed wavelength converter is numerically investigated.Based on the simulation,the relationship between the SNR of the converted OFDM signal,the injection power ratio,and the frequency offset of the control OFDM signal is depicted.The concerned simulation indicate that the transfer response from the control signal to the probe signal is quite linear,but the slight imperfection will degrade the converted OFDM signal,the scheme is effective by a proper control.Secondly,it was built the experiment platform of AOWC of OFDM signal based on TMIL in a low-cost and low-end FP laser,conducted an experimental study on various aspects of this scheme,including: output optical spectra of the FP laser with or without TMIL,frequency responses of AOWC using TMIL,transfer function of AOWC using TMIL,tolerance to the imperfection of TMIL,capacity of the AOWC using TMIL,and power penalty after AOWC.The experiment results show that this scheme is effective for the AOWC of OFDM signal,it can provide a big frequency response bandwidth which is not limited by the low electrical modulation bandwidth of the FP laser,a linear transfer function,a high performance tolerance,a system capacity larger than 40Gb/s,and a power penalty less than 3dB.Thirdly,it was built the experiment platform of all-optical wavelength multicasting(AOWM)of OFDM signal based on multi-mode injection locking(MMIL)in a low-cost and low-end FP laser.It was also experimentally researched the performance of the proposed wavelength multicasting,and it was implemented the first experimental demonstration of 5×20.41-Gb/s all-optical wavelength multicasting of OFDM signals by using the scheme.The averaged power penalty is 2.8 dB at the FEC BER limit of 2.3 × 10-3.