Research On Balanced Receive Of 40G DPSK Module

For the great requirement of bandwidth at present, communication system looks forward to high speed, big capacity and long distance.40G would be the most pivotal technique for the next generation communication network. It is necessary for transmission network to stride forward to 40G.Transmission code choice is the key technology for 40G. DPSK adopts balanced receiver, the receiver sensitivity is 3dB higher than OOK. As the optical intensity maintains constant during the transmission, it is highly tolerant for optical non-linearities. So, DPSK is extended for long-distance transmission.40Gbps DPSK transponder module is designed based on "40Gb 300 pin Transponder Multi-Source Agreement (MSA)". Module’s receiving channel consists of delay line interferometer (DLI) and balanced receiver. It has a great effect on the whole system performance if DLI don’t work on the best conditions that would result in OSNR penalty. So, auto-control of DLI is the key technology for 40Gbps DPSK module. Auto-control procedure of DLI is carried out in two stages:coarse tuning and fine tuning. Coarse tuning can be realized through searching the maximum ratio of two optical currents that balanced receiver converts the output power of DLI to. The point with maximum ratio of two optical currents makes DLI to work on the best conditions. Using the error signals of Forward Error Correction (FEC) can realize the fine tuning of DLI.Chapter 1 of this thesis, analyses the latest applications of 40Gbps systems and design actualities of modules; chapter 2 points out DPSK format code is better for long distance transmission comparing with several important 40Gbps format codes; chapter 3 introduces the whole structure of DPSK module, and components of transmit channel and receive channel; chapter 4 is about the structure and parameters of DLI; chapter 5 selects the project of using current ratio to realize coarse tuning and FEC to fine tuning comparing with several differents control methods of DLI; chapter 6 is about the detail design of different control circuits; chapter 7 is experiment datas and result analysis. It concludes that it is completely feasible using current ratio to control DLI; chapter 8 looks forward to the future works.