To meet the ever-increasing demand for data traffic, the simplified coherent optical communications, which exhibit the advantages of low cost, low power consumption and high capacity, have garnered the widespread attention for short-reach optical communications applications. To further reduce the cost of coherent optical transmissions, we for the first time propose and demonstrate the capability of non-integer-oversampling clock data recovery (CDR) to process the noise-shaped signals which is robust to the quantization noise when using cheap digital-to-analog converters (DACs). The 192-Gbps dual-polarization quadrature amplitude modulation- 16 (DP-QAM-16) transmissions are experimentally realized by jointly implementing the noise shaping (NS) technique and 4/3 samples per symbol (sps) CDR processing. Experimental results indicate that 1.2- and 1-dB Q factor gains have been achieved by using the proposed simplified coherent optical transmission structure, under the constraints of 3- and 4-bit quantization respectively. We believe that the joint implementation of NS and non-integer-oversampling CDR is promising for simplifying the coherent optical transmissions for low-cost optical communications applications.
KEYWORDS: Single mode fibers, Digital signal processing, Receivers, Modulation, Signal detection, Distortion, Signal to noise ratio, Laser sintering, Frequency division multiplexing, Dispersion
Key digital signal processing (DSP) techniques with advanced modulation formats are proposed and discussed in O-band/ C-band beyond 100G signal transmission with low cost intensity modulation and direct detection (IM/DD). Enabling by DSP in the transceiver, beyond 100G PAM, DMT and Spectra efficient frequency division multiplexing (SEFDM) signal transmission are demonstrated in optical short reach for mobile fronthaul.
KEYWORDS: Digital signal processing, Field programmable gate arrays, Orthogonal frequency division multiplexing, Modulation, Receivers, Wavelength division multiplexing, Single mode fibers, Signal attenuation, Optical amplifiers, Laser sintering
In this paper, we review our recent research progresses on real-time orthogonal frequency division
multiplexing (OFDM) transmission based on FPGA. We successfully demonstrated four-channel
wavelength-division multiplexing (WDM) 256.51Gb/s 16-ary quadrature amplitude modulation
(16QAM)-OFDM signal transmission system for short-reach optical amplifier free inter-connection with
real-time reception. Four optical carriers are modulated by four different 16QAM-OFDM signals via
10G-class direct modulation lasers (DMLs). We achieved highest capacity real-time reception optical OFDM
signal transmission over 2.4-km SMF with the bit-error ratio (BER) under soft-decision forward error
correction (SD-FEC) limitation of 2.4×10-2. In order to achieve higher spectrum efficiency (SE), we
demonstrate 4-channel high level QAM-OFDM transmission over 20-km SMF-28 with real-time reception.
58.72-Gb/s 256QAM-OFDM and 56.4-Gb/s 128QAM-OFDM signal transmission within 25-GHz grid is
achieved with the BER under 2.4×10-2 and real-time reception.
KEYWORDS: Digital signal processing, Orthogonal frequency division multiplexing, Field programmable gate arrays, Receivers, Modulation, Signal detection, Polarization, Singular optics, Transmitters, Optical filters
In this paper, we review our recent research progresses on real-time orthogonal frequency division multiplexing (OFDM) transmission and reception. We successfully realized the transmission and reception of real-time 100Gbps dual optical carrier 16-ary quadrature amplitude modulation (16QAM)-OFDM with direct detection for ultra-short fiber transmission. And we also successfully demonstrated the transmission and reception of real-time 100Gbps single-band coherent optical dual polarization (DP)-16QAM-OFDM signal for the first time with coherent detection. The measured bit error ratio (BER) for 100Gbps single-band coherent optical DP-16QAM-OFDM signal is less than 3.8×10-3 after 200-km standard single mode fiber (SSMF) without electrical dispersion compensation (EDC).
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