Straight-Line Dual-Polarization PSK Transmitter with Polarization Differential Modulation

Shota ISHIMURA  Kosuke NISHIMURA  Yoshiaki NAKANO  Takuo TANEMURA  

Publication
IEICE TRANSACTIONS on Communications   Vol.E104-B   No.5   pp.490-496
Publication Date: 2021/05/01
Publicized: 2020/10/27
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2020EBP3124
Type of Manuscript: PAPER
Category: Fiber-Optic Transmission for Communications
Keyword: 
coherent optical communications,  digital signal processing,  dual-polarization modulator,  

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Summary: 
Coherent transceivers are now regarded as promising candidates for upgrading the current 400Gigabit Ethernet (400GbE) transceivers to 800G. However, due to the complicated structure of a dual-polarization IQ modulator (DP-IQM) with its bulky polarization-beam splitter/comber (PBS/PBC), the increase in the transmitter size and cost is inevitable. In this paper, we propose a compact PBS/PBC-free transmitter structure with a straight-line configuration. By using the concept of polarization differential modulation, the proposed transmitter is capable of generating a DP phase-shift-keyed (DP-PSK) signal, which makes it directly applicable to the current coherent systems. A detailed analysis of the system performance reveals that the imperfect equalization and the bandwidth limitation at the receiver are the dominant penalty factors. Although such a penalty is usually unacceptable in long-haul applications, the proposed transmitter can be attractive due to its significant simplicity and compactness for short-reach applications, where the cost and the footprint are the primary concerns.