JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 24, NO. 3,MARCH 2006 1543 Influence of Random DC Offsets on Burst-Mode Receiver Sensitivity Peter Ossieur, Member, IEEE, Tine De Ridder, Student Member, IEEE, Xing-Zhi Qiu, Member, IEEE, and Jan Vandewege, Member, IEEE Abstract—This paper presents the influence of random direct current (dc) offsets on the sensitivity of dc-coupled burst-mode receivers (BMRxs). It is well known that a BMRx exhibits a noisy decision threshold, resulting in a sensitivity penalty. If the BMRx is dc coupled, an additional penalty is incurred by random dc offsets. This penalty can only be determined for a statistically significant number of fabricated BMRx samples. Using Monte Carlo (MC) simulations and a detailed BMRx model, the relationship between the variance of this random dc offset, the resulting sensitivity penalty, and BMRx yield (the fraction of fabricated BMRx sam- ples that meets a given sensitivity specification) is evaluated as a function of various receiver parameters. The obtained curves can be used to trade off BMRx die area against sensitivity for a given yield. It is demonstrated that a thorough understanding of the relationship between BMRx sensitivity, BMRx yield, and the variance of the random dc offsets is needed to optimize a dc- coupled BMRx with respect to sensitivity and die area for a given yield. It is shown that compensation of dc offsets with a resolution of 8 bits results in a sensitivity penalty of 1 dB for a wide range of random dc offsets. Index Terms—Avalanche photodiodes, bit error rate (BER), burst-mode receiver (BMRx), optical access network, optical receiver. I. I NTRODUCTION B URST-MODE receivers (BMRxs) [1]–[4] are an impor- tant component in passive optical networks (PONs). PON is an optical transmission technology intended for use in the access network. In PONs, the capacity of the fiber plant is shared among a group of subscribers (see Fig. 1). The upstream traffic (from the subscribers to the central office) of all these subscribers is typically combined in a time division multiple access (TDMA) scheme. A BMRx is used in the central office of the PON to handle this TDMA upstream communication. A BMRx is needed as the signal arriving at the central of- fice consists of a succession of packets with widely varying amplitudes [1]. The adoption of the ITU-T G.984.2 standard [5] [so-called gigabit-capable passive optical network (GPON)] and the IEEE 802.3ah standard {so-called gigabit-capable Ethernet passive optical network [(G)EPON]} [6] has intensified the research aimed at developing gigabit-capable BMRxs, with an emphasis on achieving high sensitivity and dynamic range [7]–[11]. In- deed, successful and economical deployment of PONs requires Manuscript received September 21, 2005; revised November 10, 2005. The authors are with the INTEC_design Laboratory, Ghent University, Ghent B-9000, Belgium (e-mail: peter.ossieur@intec.ugent.be; tine.deridder@ intec.ugent.be; xingzhi.qiu@intec.ugent.be; jan.Vandewege@intec.ugent.be). Digital Object Identifier 10.1109/JLT.2005.863294 Fig. 1. Overview of a typical passive optical network. OLT = optical line termination, ONU = optical network unit, BMRx = burst-mode receiver, BMLD = burst-mode laser driver. Fig. 2. Typical input signal of a BMRx when employed in the optical line termination of a PON. large physical reach (distance between the subscriber and the central office) and especially large splitting factors (the number of subscribers served by a single PON) [12]. This physical reach and splitting ratio are largely determined by the dynamic range and sensitivity of the BMRx [12]–[14]. Hence, it is important to maximize the sensitivity and the dynamic range of the BMRx. Therefore, one has to thoroughly understand and quantify all factors that could give rise to sensitivity penalties due to the bursty nature of the optical signal arriving at the optical line termination. This paper investigates the reduction of sensitivity due to random direct current (dc) offsets. Indeed, to the extent of the author’s knowledge, the impact of random dc offsets on the sensitivity of BMRxs (and more, in general, optical re- ceivers) has never been reported upon before in open literature. As mentioned above, the upstream signal over a PON con- sists of a rapid succession of packets with varying amplitudes. Hence, the decision threshold needed to make a difference between a received 1 and a received 0 differs from one packet to another packet (see Fig. 2). Thus, a BMRx needs to extract a decision threshold from each incoming packet. This is typically done during a few bits (called the preamble) at the beginning of each packet. In this paper, a very short guard time between packets is assumed. This corresponds to the GPON case (e.g., a guard time as short as 25.6 ns is allowed at 1.25 Gb/s) but is unlike the situation for EPON, where long guard times in com- bination with 8B/10B coding allow for alternating current (ac) 0733-8724/$20.00 © 2006 IEEE