Hungkei Keith Chow

Energy-efficiency improvements for optical access

This article discusses novel approaches to improve energy efficiency of different optical access technologies, including time division multiplexing passive optical network (TDM-PON), time and wavelength division multiplexing PON (TWDM-PON), point-to-point (PTP) access network, wavelength division multiplexing PON (WDM-PON), and orthogonal frequency division multiple access PON (OFDMA-PON). These approaches include cyclic sleep mode, energy-efficient bit interleaving protocol, power reduction at component level, or frequency band selection. Depending on the target optical access technology, one or a combination of different approaches can be applied.

A low-energy rate-adaptive bit-interleaved passive optical network

Energy consumption of customer premises equipment (CPE) has become a serious issue in the new generations of time-division multiplexing passive optical networks, which operate at 10 Gb/s or higher. It is becoming a major factor in global network energy consumption, and it poses problems during emergencies when CPE is battery-operated. In this paper, a low-energy passive optical network (PON) that uses a novel bit-interleaving downstream protocol is proposed. The details about the network architecture, protocol, and the key enabling implementation aspects, including dynamic traffic interleaving, rate-adaptive descrambling of decimated traffic, and the design and implementation of a downsampling clock and data recovery circuit, are described. The proposed concept is shown to reduce the energy consumption for protocol processing by a factor of 30. A detailed analysis of the energy consumption in the CPE shows that the interleaving protocol reduces the total energy consumption of the CPE significantly in comparison to the standard 10 Gb/s PON CPE. Experimental results obtained from measurements on the implemented CPE prototype confirm that the CPE consumes significantly less energy than the standard 10 Gb/s PON CPE.

Multi-user encoding for forward error correction in passive optical networks

We propose a method and hardware architecture for error-correction encoding of downstream traffic in a passive optical network. The encoder can handle multiple users using multiple error-correction codes. Our solution further allows transmission of a codeword across multiple timeslots allotted to a user. his ability to spread out the user payload allows decimation of the data processing rate at the user end, leading to lower energy consumption. Hardware emulation based on the developed design shows that our multi-user encoder consumes significantly less power than a system using conventional encoders in parallel.

CBI: a scalable energy-efficient protocol for metro/access networks

This paper presents a scalable energy-efficient MAC/PHY protocol for building a metro/access network. The proposed cascaded bit-interleaving (CBI) protocol extends the previously reported bit-interleaving concept to a multi-level paradigm. Moreover, a 40Gb/s 3-level electrical duobinary based physical layer scheme has been proposed for cost and energy saving, especially for end terminals. We compared two implementation approaches in terms of optical budget and transmission penalties. The initial estimate from the proof-ofconcept full-custom ASIC design shows that an ultra-low power metro/access network can be realized.

Power scalable descrambling methods for bit-interleaved TDM networks

A broadcast network in which a sender transmits to several receivers, each receiving different data, is considered. A time division multiplexing scheme based on bit-interleaving, where each receiver is given an allocation of bit positions occurring in periodic intervals within the frame, is assumed. In previous work, bit-interleaving was shown to yield 30× power savings. However, to enable bit-interleaving, a descrambler design capable of operating on the downsampled data corresponding to the receivers allocation is required. Several efficient methods are presented to accomplish this task both for fixed and variable allocations to the receivers. The proposed methods can be used to implement a power-scalable, low complexity, and low cost descrambler that operates at the receivers data rate, which is typically far lower than the total transmission rate.

A “Power-on-demand” optical transceiver design for green access and in-home network applications

In this paper, we present an optical transceiver that is capable of adaptively optimizing its power consumption according to transmission conditions. It consumes <;25 mW of power for 0-40 km Gigabit data transmission.

Low-power current-equalised optical transmitter for below-threshold-biasing VCSEL operation

A novel optical driver circuitry is proposed to improve the optical eye diagram for the VCSEL operating below the threshold current. The circuitry enables the operator to balance between the energy efficiency and optical signal quality.