3.5 Gb/s burst-mode clock phase aligner for gigabit passive optical networks

Abstract

Fiber to the Home (FTTH) has been proven to be an efficient medium for voice, audio, and video transfer. Passive Optical Networks (PONs) are being studied as an upgradeable and low-cost solution to the problem of limited bandwidth in local access networks in the medium of FTTH. In PONs, multiple users share the fiber infrastructure in a pointto-multipoint (P2MP) network topology. The P2MP nature of networks cause the data packets from each user to undergo different amplitude, phase, and frequency variations -resulting in burst-mode traffic at the receiving end of the network. This consequently creates new challenges for the design of optical receivers.We design and experimentally demonstrate a 5 Gb/s burst-mode clock phase aligner (BM-CPA) featuring automatic phase acquisition with forward-error correction using (64, 57) Hamming codes. This BM-CPA is implemented with commercially available evaluation boards and provides instantaneous (0-bit) phase acquisition with packet loss ratio < 10and bit error rate < 10 −10 for any phase step (±2π rads) between consecutive packets.Implementation of a Reed-Solomon(255, 239) code is also investigated. Our design is based on an oversampling algorithm and can be operated in two configurations: BM-CPA with a SONET CDR and BM-CPA with a local oscillator. We conclude by discussing various possible extensions to the device, based on the promising results.ii