High Speed All Optical Nyquist Signal Generation and Full-band Coherent Detection

Abstract

Spectrum efficient data transmission is of key interest for high capacity optical communication systems considering the limited available bandwidth. Transmission of the high speed signal with higher-order modulation formats within the Nyquist bandwidth using coherent detection brings attractive performance advantages. However, high speed Nyquist signal generation with high order modulation formats is challenging. Electrical Nyquist pulse generation is restricted by the limited sampling rate and processor capacities of digital-to-analog convertor devices, while the optical Nyquist signals can provide a much higher symbol rate using time domain multiplexing method. However, most optical Nyquist signals are based on direct detection with simple modulation formats. Here we report the first experimental demonstration of high speed all optical Nyquist signal generation based on Sinc-shaped pulse generation and time-division multiplexing with high level modulation format and full-band coherent detection. Our experiments demonstrate a highly flexible and compatible all optical high speed Nyquist signal generation and detection scheme for future fiber communication systems.

A Survey of Optical Carrier Generation Techniques for Terabit Capacity Elastic Optical Networks

“…The ideal Nyquist filter that provides zero ISI, have a rectangular spectrum and a bandwidth equal to the symbol rate [64], [75]. High speed Nyquist signal generation is challenging, as the electrical pulse generation is restricted by the sampling rate and the bandwidth of DACs as well as the processing capabilities [76]. Super-flat optical frequency combs, with a rectangular spectrum and linear phase, can provide high quality Nyquist pulses [75].…”

“…In [75], Soto et al demonstrated the generation of optical sinc-shaped Nyquist pulses of exceptional quality, using flat rectangular frequency combs, providing zero roll-off, minimum post-modulation spectral broadening and 1% deviation from ideal sinc shape. The authors in [76] demonstrated full band coherent detection of Nyquist pulses employing QPSK modulation and optical time division multiplexing (OTDM). Similarly, sinc-shape pulses can also be multiplexed in the frequency domain, following Nyquist WDM transmission scheme, where pulses can be generated and modulated for each carrier.…”

“…Such findings can be very useful in flexible operations of combs, where we want to change the number of lines or frequency spacing. [76] and multiple MZMs in cascade [105] have been used, driven by single or multiple frequency RF signals. A summary of recent relevant reports can be found in Table V.…”

“…IM based combs ( Fig. 13 (f)) have also been used to generate sinc pulses for NWDM/OTDM systems, due to rectangular spectral profile of the comb [75], [76], [114]. Sinc pulses, with pulse widths ranging from 3.5 ps to 8.75 ps, repetition rates from 52.5 ps to 157 ps and duty cycles from 2.2% up to 16.6%, were experimentally generated.…”

All-optical generation of DFT-S-OFDM superchannels using periodic sinc pulses

“…Nakazawa et al have also proposed a "Nyquist Laser" with spectral shaping inside the mode-locked cavity [12], which produces similar sinc-shaped pulses. Zhang et al have recently built a single wavelength OrthTDM system using comb lines generated by a CW laser with external modulator and filter, followed by a modulator then an optical OrthTDM multiplexer similar to Nakazawa's arrangement, but using a coherent receiver [13].…”