On the usage of FDLs in optical parallel transmission to support high speed Ethernet

Parallel transmission in the optical layer can enable a scalable network migration from low speed interfaces to high speed serial interfaces, such as 100Gbps Ethernet, as they become available. It is based on the principle of inverse-multiplexing which distributes high speed data stream into multiple low rate optical paths. The main challenge in parallel transmission is the differential delay experienced by different paths. Thus so far, electronic buffering has been widely used to compensate for differential delay. However, at very high speed line rates, such as 40Gbps or even 100Gbps, electronic buffering maybe a challenge. In this paper, we study the usage of Fiber Delay Lines (FDLs) for compensation of differential delay in optical parallel transmission in support of high speed Ethernet services. To this end, we formulate the problem of optimal usage of FDLs in optical networks an Integer Linear Programming (ILP) problem. The results are encouraging as they show that discrete nature of delay provided by FDL buffers is not as limiting as expected, and that FDLs carry potential to enable optical parallel transmission without the need to provide large electronic buffers.