Rectangular QPSK for generation of optical eight-ary phase-shift keying

Guo Wei Lu*, Takahide Sakamoto, Tetsuya Kawanishi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Quadrature phase-shift keying (QPSK) is usually generated using an in-phase/quadrature (IQ) modulator in a balanced driving-condition, showing a square-shape constellation in complex plane. This conventional QPSK is referred to as square QPSK (S-QPSK) in this paper. On the other hand, when an IQ modulator is driven in an un-balanced manner with different amplitudes in in-phase (I) and quadrature (Q) branches, a rectangular QPSK (R-QPSK) could be synthesized. The concept of RQPSK is proposed for the first time and applied to optical eight-ary phaseshift keying (8PSK) transmitter. By cascading an S-QPSK and an R-QPSK, an optical 8PSK could be synthesized. The transmitter configuration is based on two cascaded IQ modulators, which also could be used to generate other advanced multi-level formats like quadrature amplitude modulation (QAM) when different driving and bias conditions are applied. Therefore, the proposed transmitter structure has potential to be deployed as a versatile transmitter for synthesis of several different multi-level modulation formats for the future dynamic optical networks. A 30-Gb/s optical 8PSK is experimentally demonstrated using the proposed solution.

Original languageEnglish
Pages (from-to)18479-18485
Number of pages7
JournalOptics Express
Issue number19
Publication statusPublished - 2011 Sept 12
Externally publishedYes

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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