On the Use of Gaussian Approximation in Analyzing the Performance of Optical Receivers

Abstract

The analytical calculation of the bit error rate (BER) of digital optical receivers that employ avalanche photodiodes (APDs) is challenging due to 1) the stochastic nature of the avalanche photodiode's impulse-response function and 2) the presence of intersymbol interference (ISI). At ultrafast transmission rates, ISI becomes a dominant component of the BER, and its effect on the BER should be carefully addressed. One solution to this problem, termed the bit-pattern-dependent (PD) approach, is to first calculate the conditional BER given a specific bit pattern and then average over all possible bit patterns. Alternatively, a simplifying method, termed the bit-pattern-independent (PI) approach, has been commonly used whereby the average bit stream is used to calculate the distribution of the receiver output, which, in turn, is used to calculate the BER. However, when ISI is dominant, the PI approximation is inaccurate. Here, the two approaches are analytically compared by analyzing their asymptotic behavior and their bounds. Conditions are found to determine when the PI method overestimates the BER. The BER found using the PD method exponentially decays with the received optical power, whereas for the PI approach, the BER converges to a constant, which is unrealistic. For an InP-based APD receiver with a 100-nm multiplication layer, the PI method is found to be inaccurate for transmission rates beyond 20 Gb/s.

Performance of Non-Line of Sight Underwater Optical Wireless Communication Links with Spatial Diversity

“…In addition, methods based on the expectation on the values of previous bits may also be employed [39], which can utilize the GA [40]. Here, we use a particular bit sequence to produce an upper bound, which is known to be effective for UOWC [28].…”

Performance of Non-Line of Sight Underwater Optical Wireless Communication Links with Spatial Diversity

“…Since, the effects of ISI on the current bit are reduced as the previous bits become further in the past, a truncation of the number of bits is employed as 26) and ( 34) respectively. captured here by methods based on the expectation on the values of previous bits may also be employed [39], which can utilize the GA [40]. Here, we use a particular bit sequence to produce an upper bound, which is known to be effective for UOWC [28].…”

Optical Code-Division Multiplexing (OCDM) Networks Adopting Code-Shift Keying/Overlapping PPM Signaling: Proposal and Performance Analysis

“…Avalanche photodiodes (APDs) are commonly used in many high-speed optical receivers due to their internal optoelectronic gain [6]. The three main competing factors that govern APDbased optical receivers performance at high speed are: (i) the avalanche noise of the APD; (ii) the buildup time which limits APD speed by inducing intersymbol interference (ISI); and (iii) the APD dark current [7].…”