Author Affiliations
1Peng Cheng Laboratory, Shenzhen, China2Shanghai Jiao Tong University, State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Electronic Engineering, Shanghai, China3University of L’Aquila, Department of Physical and Chemical Sciences, L’Aquila, Italyshow less
Fig. 1. (a) Schematic of generation and predistortion procedures of LUT. , transmitted training symbols; , recovered training symbols; , the difference between the known transmitted symbols and the recovered symbols; , the counter; , averaged error; , transmitted payload symbols; , the predistorted symbols. (b) Schematic block diagram of DRE. , input signal needed to be converted to analog; , quantized version of ; , effective quantization error; , the round-off error; , an integer control sequence; DQ, dynamic quantization; Δ, DAC output step size; , the dynamic quantization error; , the combined frequency response of the channel and the matched filtering.
Fig. 2. Pattern error versus pattern index for PAM-4 signal in the following experiment.
Fig. 3. (a) Combined response of the channel and the matched filtering. (b) Electrical spectra of quantized signals for 124-GBd PAM-4 modulation with and without DRE.
Fig. 4. (a) Experimental setup. DFB, distributed feedback; AWG, arbitrary waveform generator; MZM, Mach–Zehnder modulator; SSMF, standard single-mode fiber; SOA, semiconductor optical amplifier; VOA, variable optical attenuator; PD, photodiode; RTO, real-time oscilloscope. (b) DSP procedures implemented at the transmitter and receiver sides. RRC, root-raised cosine; LUT, look-up-table; DRE, digital resolution enhancer. (c) Optical spectrum of 124-GBd PAM-4 signal. (d) Received electrical spectrum of 124-GBd PAM-4 signal.
Fig. 5. Measured BERs versus ROP in the case of 2-km SSMF transmission for (a) 124-GBd PAM-4, (e) 124-GBd PAM-6, and (i) 112-GBd PAM-8 signals. Measured BERs versus PNoB in the case of 2-km SSMF transmission for (b) 124-GBd PAM-4, (f) 124-GBd PAM-6, and (j) 112-GBd PAM-8 signals. Electrical spectra with and without DRE of (c) 124-GBd PAM-4 signal using a 3-bit DAC, (g) 124-GBd PAM-6 signal using a 3.5-bit DRE, and (k) 112-GBd PAM-8 signal using a 4-bit DRE. Temporary amplitudes versus sample index of (d) 124-GBd PAM-4 signal with a 3-bit DAC and DRE, (h) 124-GBd PAM-6 signal with a 3.5-bit DAC and DRE, and (l) 112-GBd PAM-8 signal with a 4-bit DAC and DRE.
Fig. 6. Measured BERs versus PNoB in the 40-km SSMF transmission for (a) 124-GBd OOK, (e) 124-GBd PAM-3, and (i) 124-GBd PAM-4 signals. Measured BERs versus ROP in the 40-km SSMF transmission for (b) 124-GBd OOK, (f) 124-GBd PAM-3, and (j) 124-GBd PAM-4 signals. Electrical spectra with and without DRE of (c) 124-GBd OOK with a 1.5-bit DAC, (g) 124-GBd PAM-3 with a 2-bit DAC, and (k) 124-GBd PAM-4 with a 3-bit DAC signals. Temporal amplitudes versus (d) 124-GBd OOK signal with a 1.5-bit DAC and DRE, (h) 124-GBd PAM-3 signal with a 2-bit DAC and DRE, and sample index (l) 124-GBd PAM-4 signal with a 3-bit DAC and DRE.
Reference | Baud rate (GBd) | Modulation format | Net data rate (Gb/s) | Band | Distance (km) | Resolution of DAC (bit) | DSP method | FEC | Ref. 28 | 28 | PAM-4 | 52.3 | C | 80 | 4 | EDC, TQNS | 7% HD-FEC | Ref. 32 | 32 | PAM-4 | 59.8 | C | 10 | 3 | Preequalization, EFNS | 7% HD-FEC | Ref. 33 | 40 | PS-PAM-4 | 74.1 | C | 3 | 3 | Preequalization, EFNS | 7% HD-FEC | Ref. 31 | 50 | 16/32/64-QAM-DMT | 91.7/114/137.5 | C | 2 | 4/5/6 | Preequalization, TQNS | 7% HD-FEC | Ref. 45 | 50 | PAM-4 | 93.5 | N/A | 0 | 3 | Preequalization, DRE | BER = , <7% HD-FEC | Ref. 36 | 50 | DFT-S-32-QAM-DMT | 93.5 | C | 2 | 5 | Preequalization, TQNS | 7% HD-FEC | Ref. 29 | 50 | DMT | 93.5 | C | 2 | 3 | Preequalization, CRD-NS | 7% HD-FEC | Ref. 37 | 55 | PAM-4 | 102.8 | C | 2 | 3 | Preequalization, CRD-NS | 7% HD-FEC | Ref. 44 | 56 | PAM-4 | 104.7 | C | 40 | 4 | THP, DRE | 7% HD-FEC | Ref. 30 | 56 | PAM-4 | 104.7 | C | 80 | 3 | CDPC, Clipping, DRE | 7% HD-FEC | Ref. 35 | 60 | PAM-4 | 112.1 | O | 40 | 4 | Preequalization, TQNS | 7% HD-FEC | This work | 124 | PAM-4 | 235.3 | O | 2 | 3 | DRE | KP4-FEC | This work | 124 | PAM-6 | 289.7 | O | 2 | 3.5 | DRE | 7% HD-FEC | This work | 112 | PAM-8 | 294.7 | O | 2 | 4 | DRE | 14% HD-FEC | This work | 124 | PAM-2 | 117.6 | O | 40 | 1.5 | LUT predistortion, DRE | KP4-FEC | This work | 124 | PAM-3 | 173.8 | O | 40 | 2 | LUT predistortion, DRE | 7% HD-FEC | This work | 124 | PAM-4 | 231.8 | O | 40 | 3 | LUT predistortion, DRE | 7% HD-FEC |
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Table 1. Comparison of high-speed IM-DD optics with low-resolution DAC.