Hardware-Efficient Coherent Digital Receiver Concept With Feedforward Carrier Recovery for M -QAM Constellations

• Published in: Journal of lightwave technology 2009-04, Vol.27 (8), p.989-999
• Main Authors: Pfau, T., Hoffmann, S., Noe, R.
• Format: Article
• Language: English
• Subjects: Algorithms; Analog-digital conversion, digital-analog conversion, pcm coding; Applied sciences; Carriers; Circuit properties; Coherent communication; Computer simulation; Constellations; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Feedback loop; Feedforward; feedforward carrier recovery; Information, signal and communications theory; Integrated optics. Optical fibers and wave guides; Laser feedback; Laser noise; Modulation, demodulation; Monte Carlo methods; Noise; Optical and optoelectronic circuits; optical communication; Optical feedback; Optical fiber communication; Optical receivers; parallel processing; phase estimation; Phase noise; Quadrature amplitude modulation; Quadrature phase shift keying; Recovery; Signal and communications theory; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Wavelength division multiplexing
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2008.2010511

This paper presents a novel digital feedforward carrier recovery algorithm for arbitrary M -ary quadrature amplitude modulation (M-QAM) constellations in an intradyne coherent optical receiver. The approach does not contain any feedback loop and is therefore highly tolerant against laser phase noise. This is crucial, especially for higher order QAM constellations, which inherently have a smaller phase noise tolerance due to the lower spacing between adjacent constellation points. In addition to the mathematical description of the proposed carrier recovery algorithm also a possible hardware-efficient implementation in a parallelized system is presented and the performance of the algorithm is evaluated by Monte Carlo simulations for square 4-QAM (QPSK), 16-QAM, 64-QAM, and 256-QAM. For the simulations ASE noise and laser phase noise are considered as well as analog-to-digital converter (ADC) and internal resolution effects. For a 1 dB penalty at BER = 10 -3 , linewidth times symbol duration products of 4.1 x 10 -4 (4-QAM), 1.4 x 10 -4 (16-QAM), 4.0 x 10 -5 (64-QAM) and 8.0 x 10 -6 (256-QAM) are tolerable.