Research On The Multi-wavelength Signals Buffering Based On DLOB And Slow Light Via Stimulated Brillouin Scattering

As the rapid developing of the optical communication,the capacity of the optical transmission has arrived to 10Tbit/s.But the frequent switching (optical-electronic-optical) is a serious bottleneck for high speed switching.Buffering is an effective method to solve the packet contention in optical domain without the conversion of "optical-electronic-optical(O/E/O)" and all-optical buffer becomes the key component in optical switching node.The all optical buffer which is based on dual loop optical buffer and SBS slow light is a novel optical buffer.The optical buffer has the advantages of stableness,compactness,low cost and easy implementation.Most of past optical buffer are experimentally demonstrated for the single wavelength,low speed signals buffering or using a frequency-routing-type time division interconnection network.The rapid growth of IP and multimedia services are driving demand for high capacity and high speed optical networks.Multi-wavelength optical buffer is more required to be investigated.In this paper,we focus on the multi wavelength signals buffering in optical buffer based on DLOB and SBS slow light under support of the "863" project and the National Nature Science Foundation.These conclusions can also be applicable for all the other SOA based re-circular all-optical buffers.What I have done during the PHD period are as follows:1.Based on the method of"curve divided",the cross gain modulation is analyzed.The method of reducing the cross talk by injecting high power control laser to SOA is presented.Under high power continuous laser,the fluctuation of the signal power caused by cross gain modulation is well restrained,the Signal Noise Ratio(SNR) is greatly improved and the Bit Error Rate(BER) is reduced obviously.A model of noise equal to the fluctuation of the signal power caused by the cross gain modulation is built.The relationship between BER and the noise in SOA are deeply studied.2.The dual wavelength signals buffering in DLOB are successfully demonstrated.The 2.5Gb/s data packets are well retrieved after they are buffered for 10 cycles corresponding to 12.Sus.An "optimal power of control laser" is presented to solve the problem of the unbalanced bits power and the unbalanced bits phase shift.When buffering the dual wavelength signals,the no uniform input power between bit "1" and "1+1"will induce unbalanced power gain inside the packet.It is impossible to store all dual-wavelength bits at the same time in this case.We solve this problem by adjusting the control signal to a suitable power level that satisfied the equation|Δφ₁-Δφ2|≤δ,δis the tolerance of the phase,difference(0.1rad).It gives a clear solution for dual wavelength signals buffering in DLOB and the method is fully demonstrated by the experiment.3.A method of"power equalization" is presented to solve the unequal bits power when buffering multi-wavelength signals.This method is that by making SOA work at its saturation point;all bits power will be approximately equal.It gives an effective way to improve the quality of dual wavelength and multi wavelength signals buffering.By using "power equalization",the buffering time of the dual wavelength signals increases from 10 cycles to 16 cycles and the power difference among the bits of 8 wavelengths signals reduced form 1:8 to 1:2 which nearly return to the fact of buffering dual wavelengths signals.4.The 8×10Gbit/s data packets buffering in DLOB is successfully demonstrated.The data packets can be retrieved after they are buffered fbr 5 cycles.One of the main problems for less buffering time is the Four Wave Mixing(FWM) in SOA.In order to reduce the impact of FWM,the method of using unequal space channels and ad the polarization matching is presented.5.A method for analyzing the dual-wavelength signals delayed via Brillouin Slow Light in an Optical Fiber is presented.The expression of Stimulated Brillouin Scattering gain and phase caused by two pumps are given.The conclusion of two pumps SBS gain and phase are not dependent are obtained.The stimulated Brillion scatter(SBS) optical spectrum in single-mode optical fiber(SMF),photosensitive fibres(PSF) and photonic crystal fibers(PCF) are.tested and measured.The different refractive indexes of fibbers cause different Brillion frequency shifts. Under two pumps,each wavelength delay of the signal can be also controlled by the other wavelength.For single wavelength,the width of 100ns pulse can be delayed from Ons to 40ns by tuning the power of the pump while for dual wavelength pumps the delay time decrease to 25ns.