Abstract
Fiber-optical networks are a crucial telecommunication infrastructure in society. Wavelength division multiplexing allows for transmitting parallel data streams over the fiber bandwidth, and coherent detection enables the use of sophisticated modulation formats and electronic compensation of signal impairments. Optical frequency combs can replace the multiple lasers used for the different wavelength channels. Beyond multiplexing, it has been suggested that the broadband phase coherence of frequency combs could simplify the receiver scheme by performing joint reception and processing of several wavelength channels, but an experimental validation in a fiber transmission experiment remains elusive. Here we demonstrate and quantify joint reception and processing of several wavelength channels in a full transmission system. We demonstrate two joint processing schemes; one that reduces the phase-tracking complexity and one that increases the transmission performance.
Highlights
Fiber-optical networks are a crucial telecommunication infrastructure in society
Optical frequency combs were originally conceived for establishing comparisons between atomic clocks[1] and as a tool to synthesize optical frequencies[2,3], but they are becoming an attractive light source for coherent fiber-optical communications, where they can replace the hundreds of lasers used to carry digital data[4]
In a lightwave communication system that uses a frequency comb in place of multiple lasers, the importance of the phaselocking of the comb lines is that all the channels suffer from similar optical phase noise—a fundamental noise source that results in one of the predominant impairments in coherent optical receivers
Summary
Fiber-optical networks are a crucial telecommunication infrastructure in society. Wavelength division multiplexing allows for transmitting parallel data streams over the fiber bandwidth, and coherent detection enables the use of sophisticated modulation formats and electronic compensation of signal impairments. One of the key advantages of frequency combs in optical communication is that the separation between consecutive lines is extremely stable This enables highspectral-efficiency transmission by minimizing the spectral guard bands between wavelength channels[5,6], and allows for an efficient pre-compensation of fiber nonlinearities[7]. Modern lightwave communication systems compensate for phase noise using digital signal processing (DSP), which is a main source of power consumption in the receiver This DSP function can be simplified by using analog methods to phase-lock the LO to the carrier, but at the cost of decreased spectral efficiency and an increased analog complexity[11,12,13]. We show that a different, joint phase-estimation scheme will increase the tolerance to rapid phase fluctuations induced by nonlinearities in frequency comb-based systems
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