Study on Tapered Multimode Interference-Based Coherent Lightwave Combiners

Zhigang WU
Katsuyuki UTAKA

Publication
IEICE TRANSACTIONS on Electronics   Vol.E88-C    No.5    pp.1005-1012
Publication Date: 2005/05/01
Online ISSN: 
DOI: 10.1093/ietele/e88-c.5.1005
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Joint Special Section on Recent Progress in Optoelectronics and Communications)
Category: Optical Passive Devices and Modules
Keyword: 
taper,  MMI,  end-facet reflection,  multi-port combiner,  

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Summary: 
In this paper we analyze the characteristics of tapered multimode interference (MMI)-based coherent lightwave combiners, and theoretically confirm that the stable and clear multimode interference images exist in the tapered MMI combiners. We present the output characteristics of 21 tapered MMI-based coherent lightwave combiners under various structures, which are useful to optimally design the combiners. In order to extend the combiner to a multi-port (N1, N > 2) configuration, a new structure with the border shapes of two tangent arcs is proposed, by which we show an output power imbalance of about 0.5 dB between different input ports of an 81 tapered coherent lightwave combiner. Due to the advantages of no end-facet reflection, easy extension to a multi-port configuration, high tolerance for fabrication errors and a compact size, the tapered MMI structure is a good candidate as a coherent lightwave combiner used in large-scale photonic integrated circuits.