Wavelength Conversions And The Integrated Chips Based On Semiconductor Optical Amplifiers

In recent years,with the rapid development of the information technologies,such as fiber to the home,cloud computing,internet of things,and data center,the demand for optical network bandwidth is explosively increasing.The data rates of the next generation optical fiber communication network will be increased to 400 Gbit/s~1 Tbit/s.The optical-electrical-optical(O-E-O)switching,which is still utilized in the current photonic network nodes,has the problems such as large power consumption and signal processing bottleneck.By contrast,all-optical switching is gradually becoming the development direction,with the advantages of high speed,low power consumption,potential low cost,etc.All-optical wavelength conversion and the related wavelength routing are important foundations for high-speed,non-blocking wavelength division multiplexing(WDM)network,because of the capability to solve the channel competition and improve the wavelength utilization.Besides,as the fabrication technology of optoelectronic integrated chips is getting mature,the optoelectronic system is developing towards photonic integrated circuit(PIC)by integrating discrete components on the same substrate.Therefore,it has gradually become a research hotspot to study the integrated high-speed all-optical wavelength converter chip with small volume and low power consumption.Among all the techniques to realize all-optical wavelength conversion,thanks to the small volume,high nonlinearities and integrated potential of semiconductor optical amplifier(SOA),the SOA-based all-optical wavelength conversion schemes have attracted a lot of interest at home and abroad.In this dissertation,we focus on the research of cross-gain and cross-phase modulation effects in SOA,as well as the ultra-fast dynamical characteristics.The SOA-based all-optical wavelength conversions and the related integrated schemes are also studied.The monolithically integrated high-speed all-optical wavelength converter and router PIC chips are designed and implemented.The main contents of this dissertation are listed as follows:1.Different optical ultra-fast nonlinear effects of SOA are studied,and a numerical model based on the nonlinear ultra-fast dynamical characteristics is built up.The basic principles of different schemes to realize SOA-based high-speed all-optical wavelength conversions are intensive analyzed.Then,a new integrated scheme of all-optical wavelength converter is proposed.The scheme utilizes the blue-shifted filtering to speed up the gain recovery of the SOA by extracting the ultra-fast chirp components,thus increasing the operation speed of the wavelength conversion.Besides,the delayed interferometer(DI)structure is used to flip over the signal polarity for the wavelength converted signal,then a high-speed wavelength conversion with non-inverted polarity can be achieved.All-optical wavelength conversions for return-to-zero(RZ)signals at10 Gbit/s~160 Gbit/s are realized by numerical simulation.The results indicate that the proposed all-optical wavelength converter structure is theoretically feasible.2.A chip structure of the four-channel high-speed all-optical wavelength converter is proposed.The mask layout of the structure is designed,and the indium phosphide(InP)monolithically integrated chip is fabricated through a multi-project wafer(MPW)run,with a size of 4.6×1.85 mm~2.The chip integrates four high-speed all-optical wavelength converters,which can be used for both all-optical unicast wavelength conversion and all-optical wavelength multicasting.The chip contains both active and passive areas,as well as straight and curved waveguides.By adding offset structures between curved waveguides,and using buffer transition structures between deep-and shallow-etched waveguides,optical propagation loss and optical feedback are reduced.By utilizing the chip,we demonstrate error-free all-optical unicast wavelength conversions for both non-return-to-zero(NRZ)and RZ signals at 40 Gbit/s,with power penalties as low as 2.3 dB and 2.7 dB,respectively.Besides,error-free 1×2 all-optical wavelength multicasting are also achieved,giving a total data capacity of 80 Gbit/s with power penalties as low as 2.5 dB for NRZ and 3.2 dB for RZ signals.3.An integrated chip structure of the 4×4 all-optical wavelength router is proposed.And the InP monolithically integrated chip is fabricated by MPW technology.The chip consists of four SOAs and one arrayed-waveguide grating router(AWGR).In the chip,all-optical wavelength conversions are realized based on the cross-gain and cross-phase modulation effects in the SOA.The conversion speed is improved by utilizing the blue-shifted filtering with the AWGR.Meanwhile,the AWGR is also used to realize the passive all-optical routing.Both 1×4 and 3×1 40 Gbit/s all-optical wavelength routings for NRZ signals are realized,with power penalties as low as 3.6 dB and 3.2 dB,respectively.4.An integrated multi-wavelength laser chip is designed and realized,based on SOA,AWG and multi-mode-interference reflector(MIR).The laser can achieve digital wavelength tuning.Compared with the traditional Fabry-Pérot structures,the proposed MIR-based reflection structure reduces the overall chip size.Besides,the output laser has a higher sidemode suppression ratio by utilizing the in-cavity AWG to double filtering than normal single filtering.The mask layout of the multi-wavelength laser is designed,and the InP monolithically integrated chip is fabricated through an MPW run.The functionality of this multi-wavelength laser chip is demonstrated in both simulation and experiment.Five wavelengths with tunable outputs are achieved in the C band.5.A chip structure of the all-optical wavelength router with distributed Bragg reflector(DBR)tunable laser source is designed.The InP monolithically integrated wavelength router chip is designed and fabricated by MPW technology.The wavelength tuning range,tuning speed and stability of the on-chip two DBR lasers with different structures are experimentally investigated.Besides,the influence of the optical feedback between the SOA and the DBR laser on the all-optical wavelength conversion is analyzed.The experimental results indicate the 9-nm and 10-nm wavelength tuning range in the C band of the two DBR lasers.Besides,error-free 20-Gbit/s all-optical wavelength conversion with the wavelength converter on the chip is achieved,with power penalty of 2 dB.