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

TLDR

Optical buffering remains a key challenge for optical packet switching, and while fiber‑delay‑line buffers are practical, their bulkiness hinders deployment. This work demonstrates a compact optical buffer achieving up to 750‑ns capacity and 50‑ns resolution by combining an InP integrated 1×16 phased‑array switch with a compact fiber‑delay‑line module based on thin‑cladding highly nonlinear fiber. The design coils 15 fibers totaling 1.2 km onto a single coin‑sized bobbin thanks to high mode confinement in the HNLF, and employs a pitch‑converting silica planar‑lightwave circuit chip to uniformly interconnect the InP switch and the delay lines. Experiments confirm variable optical buffering, successfully expanding packet intervals from 20 ns to 70 ns.

Abstract

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.