Uncoordinated Optical Multiple Access using IDMA and Nonlinear TCM PIs: Eli Yablanovitch, Rick Wesel, Ingrid Verbauwhede, Bahram Jalali, Ming Wu Students whose work is discussed here: Juthika Basak, Herwin Chan, Miguel Griot, Andres Vila Casado, Wen-Yen Weng UCLA Electrical Engineering Department-Communication Systems Laboratory

UCLA Electrical Engineering Communication Systems Laboratory2 OCDMA Coding Architecture OR channel 5 other tx Reed Solomon (255, 237) Trellis Code 1/20 int Correct extra errors Asychronous Access code Separate different transmitters 2 Gbps 93 Mbps 60 Mbps 1.2 Gbps

UCLA Electrical Engineering Communication Systems Laboratory3 The system Reed Solomon (255, 237) Trellis Code 1/20 intsync Reed Solomon (255, 237) Trellis Code 1/20 int sync Bit align OR channel 5 other tx Large feedback loop for rx synchronization BER Tester For uncoor- dinated access To distinguish between users To bring final BER to 1e-9 Initial synchroni- zation of tx-rx pair

UCLA Electrical Engineering Communication Systems Laboratory4 Experimental Setup FPGA XMIT 1 FPGA XMIT 2 FPGA XMIT 3 FPGA XMIT 4 FPGA XMIT 5 FPGA XMIT 6 AMP Optical MOD Optical MOD Optical MOD Optical MOD Optical MOD Optical MOD FPGA RCV 1 Optical to Electrical D Flip-Flop

UCLA Electrical Engineering Communication Systems Laboratory5 Six Users

UCLA Electrical Engineering Communication Systems Laboratory6

UCLA Electrical Engineering Communication Systems Laboratory7 Probability of amplitudes for 6-users HeightProbability e e e e e e e-006

UCLA Electrical Engineering Communication Systems Laboratory8 Asynchronous users

UCLA Electrical Engineering Communication Systems Laboratory9 Receiver Ones Densities for this code. Number of UsersReceiver Ones Density

UCLA Electrical Engineering Communication Systems Laboratory10 Performance results FPGA implementation: In order to prove that NL-TCM codes are feasible today for optical speeds, a hardware simulation engine was built on the Xilinx Virtex2-Pro 2V20 FPGA. Results for the rate-1/20 NL-TCM code are shown next. Transfer Bound: Wen-Yen Weng collaborated in this work, with the computation a Transfer Function Bound for NL-TCM codes. It proved to be a very accurate bound, thus providing a fast estimation of the performance of the NL-TCM codes designed in this work.

UCLA Electrical Engineering Communication Systems Laboratory11 C-Simulation Performance Results: 6-user OR-MAC 6-user BER 10 -5

UCLA Electrical Engineering Communication Systems Laboratory12 6-user OR-MAC: Simulation, Bound, FPGA (no optics) 6-user BER 10 -5

UCLA Electrical Engineering Communication Systems Laboratory13 Results: observations An error floor can observed for the FPGA rate-1/20 NL-TCM. This is mainly due to the fact that, while theoretically a 1-to-0 transition means an infinite distance, for implementation constraints those transitions are given a value of 20. Trace-back depth of 35. Additional coding required to lower BER to below

UCLA Electrical Engineering Communication Systems Laboratory14 Dramatically lowering the BER : Concatenation with Outer Block Code Optical systems deliver a very low BER, in our work a is required. Using only a NL-TCM, the rate would have to be very low. A better solution is found using the fact that Viterbi decoding fails gradually, with relatively high probability only a small number of bits are in error. Thus, a high-rate block code that can correct a few errors can be attached as an outer code, dramatically lowering the BER. Block-Code EncoderNL-TCM Encoder Z-Channel Block-Code DecoderNL-TCM Decoder

UCLA Electrical Engineering Communication Systems Laboratory15 Reed-Solomon + NL-TCM : Results A concatenation of the rate-1/20 NL-TCM code with (255 bytes,247 bytes) Reed-Solomon code has been tested for the 6-user OR-MAC scenario. This RS-code corrects up to 8 erred bits. The resulting rate for each user is (247/255).(1/20) The results were obtained using a C program to apply the RS-code to the FPGA NL-TCM output. RateSum-ratepBER

UCLA Electrical Engineering Communication Systems Laboratory16 C-Simulation Performance Results: NL-TCM only, 100-user OR-MAC RateSum-ratepBER 1/ /

UCLA Electrical Engineering Communication Systems Laboratory17 Current Status Decreased optical speed from 2 to 1.2 Gbps because FPGA can’t keep up at 2 Gbps. Single Amplifier Results: 2-Amplifier system in progress. We need more amplifiers for six users. Last night, worked for 4 users, but two users need more power. UsersBER 1< ×10 -6

UCLA Electrical Engineering Communication Systems Laboratory18 Results Demonstrated scalability to 100 users in a C simulation. Working on our 6-user optical implementation.