All-Fiber Optical Frontend for a Balanced Polarization Diversity Receiver with 0.2 dB Excess Loss and High Noise Rejection

Abstract

We present an optical frontend for a polarization diversity receiver comprising an all-fiber hybrid and monolithic pin-photodiode pairs. The coupler hybrid consists of fused biconic TE/TM-splitters and a power splitter. Its excess loss is as low as 0.2 dB, and the polarization extinction is better than -17 dB in a 20 nm wavelength window. The photodiode pairs are grown on a semi-insulating substrate. The fiber-photodiode interfacing technique is based on self-aligned fiber positioning in grooved silicon chips. By simple adjustment the excess noise rejection of -46 dB up to 1 GHz is achieved.

Integrated-optic versus microoptic devices for fiber-optic telecommunication systems: a comparison

“…All-fiber polarization-diversity hybrids, as shown in Fig. 8, have been fabricated by AT&T [18], using side-polishing techniques, and by Daimler-Benz [20], using fused-fiber tech- nology. All-fiber hybrids offer excellent insertion losses of 0.2-0.7 dB and ultra-low reflection, but they show weak polarization-extinction ratios of around 15 dB.…”

“…The critical component in the fused-fiber hybrid is the polarization splitter [19]. Usable bandwidths are 17 nm for the fused-fiber technology [20] and over 100 nm for the side-polishing technique [18]. The side polishing technique, however, may show serious reliability problems due to aging of the epoxy which forms the coupling layer between both fibers.…”

“…A side polished version of a fiber polarization splitter (a) is shown on top[18]. The second example (b) is made with the aid of a fused fiber technique[20].…”

Ultra fabrication-tolerant fully packaged micro-optical polarization diversity hybrid

“…Whereas, in the past, polarization diversity hybrids were assembled using separate components, the drive for cost and size reduction has stimulated a trend toward either all-fiber [2], [3], monolithically integrated [4]- [9], or completely micro-optical [lo]-[ 151 polarization diversity hybrids. All-fiber hybrids [2], [3] offer low losses (0.2-0.6 dB), but polarization extinction ratios are weak (typ. 15 dB) and reliability problems may be encountered.…”