Large-Capacity Compact Optical Buffer Based on InP Integrated Phased-Array Switch and Coiled Fiber Delay Lines

Optical buffering has been one of the major technical challenges in realizing optical packet switching (OPS) routers. While fiber-delay-line-based (FDL) buffers are the most practical and realistic solution to offer useful amount of capacity, the bulkiness of long FDLs and optical switches has been the main obstacle to practical implementation. This paper demonstrates a compact optical buffer with up to 750-ns capacity and 50-ns temporal resolution by using an InP integrated 1×16 optical phased-array switch and compact FDL module based on thin-cladding highly nonlinear fiber (HNLF). Owing to the high mode confinement inside HNLF, 15 fibers with the total length of 1.2 km are coiled onto a single bobbin with a coin-sized footprint without increasing the propagation loss. At the interface between the InP switch and FDLs, a pitch-converting silica planar-lightwave circuit chip is employed to achieve 16-port simultaneous uniform interconnection. Using the developed module, variable optical buffering experiment is demonstrated, where the packet intervals are expanded from 20 to 70 ns successfully.