Design of simultaneous bidirectional transceiver module for a QSFP standard based optical link

Abstract

Parallel optical interconnects recently have emerged as one of the most promising solutions for replacing the metal-based electrical links which have signal transmission limitations in terms of physical quantity as well as link capacity. Quad Small Form-factor Pluggable (QSFP) transceiver specification was introduced by Multiple Source Agreement group (MSA) first time in 2004. QSFP is designed for many applications such as Ethernet, Fiber channel, InfiniBand, and synchronous optical network (SDH/SONET). QSFP optical links have been developed rapidly and even commercialized for many applications especially in high performance computing systems. However, all the reported QSFP are based on the conventional optical interconnection transceiver module structure where up- and down-link signals are transmitted independently using two optical fibers. Simultaneous signaling is achieved by using dedicated “transmit” and “receive” channels meaning utilize only half capacity of an optical fiber. Utilizing a single channel for the transmit/receive operation reduces channel complexities by reducing the number of fibers deployed for a particular optical link. Hence, in order to achieve a compacter, lower cost, and less complex QSFP link, using a single channel for simultaneous transmit/receive (bidirectional) operation is desirable. Recently many efforts on making high-density, high speed parallel optical module have been reported. However, almost of the reported optical modules use one wavelength for signal transmission, thus, limiting their integration capabilities for denser, more compact, and more robust optical interconnect applications. Although, several works have reported implementation of simultaneous bidirectional signaling, the structures utilize either specialized transceiver chips or filters which require complex design structures and careful design rules. Thus, to reduce cost and design complexities, it is imperative to design simple, compact, and high speed tra...