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Optical Fibers and Communications|12 Article(s)
Bidirectional intensity modulated/direct detection optical OFDM WDM-PON system
Alhalabi Mahmoud, Taspinar Necmi, and El-Nahal Fady I.
In this paper, we have evaluated a bidirectional wavelength division multiplexing passive optical network (WDM-PON) employing intensity modulated/direct detection optical orthogonal frequency division multiplexing (IM/DD-OFDM). The proposed system employs 100 Gbit/s 16 quadrature amplitude modulation (16-QAM) downstream and 5 Gbit/s on-off keying (OOK) upstream wavelengths, respectively. The proposed system is considered low-cost as non-coherent IM/DD OFDM technology and a simple reflective semiconductor optical amplifier (RSOA) colorless transmitter are employed and no dispersion compensating fiber (DCF) is needed. Based on the bit error rate (BER) results of WDM signals, the proposed WDM-PON system can achieve up to 1.6 Tbit/s (100 Gbit/s/λ × 16 wavelengths) downstream transmission over a 30 km single mode fiber (SMF). In this paper, we have evaluated a bidirectional wavelength division multiplexing passive optical network (WDM-PON) employing intensity modulated/direct detection optical orthogonal frequency division multiplexing (IM/DD-OFDM). The proposed system employs 100 Gbit/s 16 quadrature amplitude modulation (16-QAM) downstream and 5 Gbit/s on-off keying (OOK) upstream wavelengths, respectively. The proposed system is considered low-cost as non-coherent IM/DD OFDM technology and a simple reflective semiconductor optical amplifier (RSOA) colorless transmitter are employed and no dispersion compensating fiber (DCF) is needed. Based on the bit error rate (BER) results of WDM signals, the proposed WDM-PON system can achieve up to 1.6 Tbit/s (100 Gbit/s/λ × 16 wavelengths) downstream transmission over a 30 km single mode fiber (SMF).
Optoelectronics Letters
- Publication Date: Jan. 01, 2023
- Vol. 19, Issue 2, 83 (2023)
Construction and performance analysis of variable weight zero cross correlation Latin square code for spectral amplitude coding OCDMA systems
Yan LIU, Chuanqi LI, and Ye and LU
The selection of appropriate codes for an optical code division multiple access (OCDMA) network, which determines the maximum number of users and bit error rate (BER) supported by the system, is crucial. This study proposed a variable weight zero cross-correlation Latin square (VW-ZLS) code for spectral amplitude coding (SAC)-OCDMA systems, which offers high autocorrelation and zero cross-correlation, while providing differentiated quality of service (QoS) features. Using direct detection (DD) technology, the data rate of the proposed VW-ZLS code reached 4.8 Gbit/s under the condition that BER does not exceed 10-9. This was 0.5 Gbit/s higher than that of zero cross-correlation magic square variable weight optical orthogonal code (ZMS-VWOOC) with the same cross-correlation characteristics. Further, simulation results showed that in SAC-OCDMA system, the VW-ZLS code was better than ZMS-VWOOC and exhibited excellent performance. The selection of appropriate codes for an optical code division multiple access (OCDMA) network, which determines the maximum number of users and bit error rate (BER) supported by the system, is crucial. This study proposed a variable weight zero cross-correlation Latin square (VW-ZLS) code for spectral amplitude coding (SAC)-OCDMA systems, which offers high autocorrelation and zero cross-correlation, while providing differentiated quality of service (QoS) features. Using direct detection (DD) technology, the data rate of the proposed VW-ZLS code reached 4.8 Gbit/s under the condition that BER does not exceed 10-9. This was 0.5 Gbit/s higher than that of zero cross-correlation magic square variable weight optical orthogonal code (ZMS-VWOOC) with the same cross-correlation characteristics. Further, simulation results showed that in SAC-OCDMA system, the VW-ZLS code was better than ZMS-VWOOC and exhibited excellent performance.
Optoelectronics Letters
- Publication Date: Jan. 01, 2023
- Vol. 19, Issue 1, 41 (2023)
128 Gbit/s high speed optical interconnection networks in data centers by a 30 GHz Mach-Zehnder modulator
Jiajia FU, Zhan SHI, and Zhengfeng and ZHANG
A decision feedback equalization (DFE) algorithm is proposed by simplifying Volterra structure. The simplification principle and process of the proposed Volterra-based equalization algorithm are presented. With the support of this algorithm, the signal damage for four-level pulse amplitude modulation signal (PAM-4) is compensated, which is caused by device bandwidth limitation and dispersion during transmission in C-band intensity modulation direct detection (IM-DD) fiber system. Experiments have been carried out to demonstrate that PAM-4 signals can transmit over 2 km in standard single-mode fiber (SSMF) based on a 30 GHz Mach-Zehnder modulator (MZM). The bit error rate (BER) can reach the threshold of hard decision-forward error correction (HD-FEC) (BER=3.8×10-3) and its sensitivity is reduced by 2 dBm compared with traditional feedforward equalization (FFE). Meanwhile, the algorithm complexity is greatly reduced by 55%, which provides an effective theoretical support for the commercial application of the algorithm. A decision feedback equalization (DFE) algorithm is proposed by simplifying Volterra structure. The simplification principle and process of the proposed Volterra-based equalization algorithm are presented. With the support of this algorithm, the signal damage for four-level pulse amplitude modulation signal (PAM-4) is compensated, which is caused by device bandwidth limitation and dispersion during transmission in C-band intensity modulation direct detection (IM-DD) fiber system. Experiments have been carried out to demonstrate that PAM-4 signals can transmit over 2 km in standard single-mode fiber (SSMF) based on a 30 GHz Mach-Zehnder modulator (MZM). The bit error rate (BER) can reach the threshold of hard decision-forward error correction (HD-FEC) (BER=3.8×10-3) and its sensitivity is reduced by 2 dBm compared with traditional feedforward equalization (FFE). Meanwhile, the algorithm complexity is greatly reduced by 55%, which provides an effective theoretical support for the commercial application of the algorithm.
Optoelectronics Letters
- Publication Date: Jan. 01, 2023
- Vol. 19, Issue 1, 36 (2023)
VCSEL polarization modulation for pulse-per-second clock signal transfer in optical frequency distribution systems
Isoe G. M., R. Leitch A. W., and Gibbon T. B.
In this paper, a novel vertical cavity surface emitting laser (VCSEL) polarization modulation technique based on po-larization switching due to thermal heating in a single transverse mode class 10 G VCSEL at 1 310 nm is demonstrated experimentally. The inherent orthogonal polarization switching of the VCSEL carrier with changing bias is exploited in the transmission of pulse-per-second (PPS) timing clock signal. Experimental results show that PPS pulse widths of 9.97 μs and 9.98 μs are measured for back-to-back analysis and over 3.21 km of G 652 urban fibre transmission, re-spectively. This work provides a novel alternative for adoption in optical frequency and time transfer applications. In this paper, a novel vertical cavity surface emitting laser (VCSEL) polarization modulation technique based on po-larization switching due to thermal heating in a single transverse mode class 10 G VCSEL at 1 310 nm is demonstrated experimentally. The inherent orthogonal polarization switching of the VCSEL carrier with changing bias is exploited in the transmission of pulse-per-second (PPS) timing clock signal. Experimental results show that PPS pulse widths of 9.97 μs and 9.98 μs are measured for back-to-back analysis and over 3.21 km of G 652 urban fibre transmission, re-spectively. This work provides a novel alternative for adoption in optical frequency and time transfer applications.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 5, 376 (2018)
Coherent quadrature phase shift keying optical com-munication systems
El-Nahal Fady I.
Coherent optical fiber communications for data rates of 100 Gbit/s and beyond have recently been studied extensively because high sensitivity of coherent receivers could extend the transmission distance. Spectrally efficient modulation techniques such as M-ary phase shift keying (PSK) can be employed for coherent optical links. The integration of mul-ti-level modulation formats based on coherent technologies with wavelength-division multiplexed (WDM) systems is vital to meet the aggregate bandwidth demand. This paper reviews coherent quadrature PSK (QPSK) systems to scale the network capacity and maximum reach of coherent optical communication systems to accommodate traffic growth. Coherent optical fiber communications for data rates of 100 Gbit/s and beyond have recently been studied extensively because high sensitivity of coherent receivers could extend the transmission distance. Spectrally efficient modulation techniques such as M-ary phase shift keying (PSK) can be employed for coherent optical links. The integration of mul-ti-level modulation formats based on coherent technologies with wavelength-division multiplexed (WDM) systems is vital to meet the aggregate bandwidth demand. This paper reviews coherent quadrature PSK (QPSK) systems to scale the network capacity and maximum reach of coherent optical communication systems to accommodate traffic growth.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 5, 372 (2018)
DFT-spread combined with clipping method to reduce the PAPR in VLC-OFDM system
LIYang , Rui DENG, Jing HE, Song-hua HE, and Lin and CHEN
Orthogonal frequency division multiplexing (OFDM) is an attractive technique to realize high data rate in light emitting diodes (LEDs)-based visible light communication (VLC). However, high peak-to-average power ratio (PAPR) of OFDM makes VLC-OFDM very sensitive to the nonlinearity of LEDs. In this paper, the discrete Fourier transform-spread (DFT-spread) combined with clipping method is proposed to reduce the PAPR of OFDM signal in VLC system. Combining simulation with experiment, a performance comparison is made among conventional OFDM, DFT-spread-OFDM, and clipped DFT-spread-OFDM with different clipping ratios (CRs) in a single LED-based VLC system. The experimental results show that the proposed clipped DFT-spread-OFDM method can effectively improve the system performance compared with the other two methods. At the optimum signal peak-to-peak (PTP) value, by using the clipped DFT-spread-OFDM scheme with CR at 8 dB, the bit error rate (BER) of the system can be reduced from 0.003 7 to 0.000 287. Orthogonal frequency division multiplexing (OFDM) is an attractive technique to realize high data rate in light emitting diodes (LEDs)-based visible light communication (VLC). However, high peak-to-average power ratio (PAPR) of OFDM makes VLC-OFDM very sensitive to the nonlinearity of LEDs. In this paper, the discrete Fourier transform-spread (DFT-spread) combined with clipping method is proposed to reduce the PAPR of OFDM signal in VLC system. Combining simulation with experiment, a performance comparison is made among conventional OFDM, DFT-spread-OFDM, and clipped DFT-spread-OFDM with different clipping ratios (CRs) in a single LED-based VLC system. The experimental results show that the proposed clipped DFT-spread-OFDM method can effectively improve the system performance compared with the other two methods. At the optimum signal peak-to-peak (PTP) value, by using the clipped DFT-spread-OFDM scheme with CR at 8 dB, the bit error rate (BER) of the system can be reduced from 0.003 7 to 0.000 287.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 3, 229 (2018)
A novel timing synchronization for CO-OFDM systems using CAZAC sequences
Li LI, Wang YAO, Li HAN, and Gui-jun and HU
A novel symbol timing synchronization algorithm based on constant amplitude zero auto correlation (CAZAC) sequences is proposed for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. The training symbol of the proposed algorithm is comprised of four different parts, utilizing even symmetry property of each part to accomplish timing synchronization. The performance of the proposed algorithm is demonstrated by means of simulations in OFDM and CO-OFDM systems. The proposed algorithm is shown to eliminate the timing sidelobes of Park’s algorithm and has a more accurate timing estimation. In the condition of chromatic dispersion (CD), the timing metric of the proposed method still maintains its peak value at the correct timing point, while the values are almost 0 at all the other positions. Meanwhile, the timing mean square error (MSE) of the proposed algorithm remains around 10-6. A novel symbol timing synchronization algorithm based on constant amplitude zero auto correlation (CAZAC) sequences is proposed for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. The training symbol of the proposed algorithm is comprised of four different parts, utilizing even symmetry property of each part to accomplish timing synchronization. The performance of the proposed algorithm is demonstrated by means of simulations in OFDM and CO-OFDM systems. The proposed algorithm is shown to eliminate the timing sidelobes of Park’s algorithm and has a more accurate timing estimation. In the condition of chromatic dispersion (CD), the timing metric of the proposed method still maintains its peak value at the correct timing point, while the values are almost 0 at all the other positions. Meanwhile, the timing mean square error (MSE) of the proposed algorithm remains around 10-6.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 3, 225 (2018)
A novel chromatic dispersion monitoring method for 1 024 QAM fiber-optic system based on asynchronous amplitude sampling
Jia-wei SHEN, Bo ZHU, Fang-ren HU, Si-jia CHEN, and Hang and QU
A new chromatic dispersion (CD) monitoring method is proposed, and the CD monitoring is achieved on the whole range of 0—600 ps/nm. A dual-polarization (DP)-1 024 quadrature amplitude modulation (QAM) 400 Gbit/s CD monitoring system is built using OptiSystem14.0 software. With different optical signal to noise ratio (OSNR) values, different filter bandwidths or different duty cycles, the simulations are carried out. The simulation results show that this new CD monitoring method can be less affected by noise and has a high tolerance for different filter bandwidths. At the same time, this method can do effective CD monitoring on the signal with duty cycle greater than 80%. A high sensitivity in 0—200 ps/nm can be achieved using this CD monitoring method. The technique supports a wide range of data traffic and enhances operation flexibility of optical networks. A new chromatic dispersion (CD) monitoring method is proposed, and the CD monitoring is achieved on the whole range of 0—600 ps/nm. A dual-polarization (DP)-1 024 quadrature amplitude modulation (QAM) 400 Gbit/s CD monitoring system is built using OptiSystem14.0 software. With different optical signal to noise ratio (OSNR) values, different filter bandwidths or different duty cycles, the simulations are carried out. The simulation results show that this new CD monitoring method can be less affected by noise and has a high tolerance for different filter bandwidths. At the same time, this method can do effective CD monitoring on the signal with duty cycle greater than 80%. A high sensitivity in 0—200 ps/nm can be achieved using this CD monitoring method. The technique supports a wide range of data traffic and enhances operation flexibility of optical networks.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 3, 221 (2018)
Anovel soft reliability-based iterative majority-logic decoding algorithm with uniform quantization
Jian-guo YUAN, Zhe WANG, Chang-wei HE, Jin-zhao LIN, and Yu and PANG
In this paper, a novel soft reliability-based iterative majority-logic decoding algorithm with uniform quantization is proposed for regularly structured low density parity-check (LDPC) codes. A weighted measure is introduced for each check-sum of the parity-check matrix and a scaling factor is used to weaken the overestimation of extrinsic information. Furthermore, the updating process of the reliability measure takes advantage of turbo-like iterative decoding strategy. The main computational complexity of the proposed algorithm only includes logical and integer operations with the bit uniform quantization criterion. Simulation results show that the novel decoding algorithm can achieve excellent error-correction performance and a fast decoding convergence speed. In this paper, a novel soft reliability-based iterative majority-logic decoding algorithm with uniform quantization is proposed for regularly structured low density parity-check (LDPC) codes. A weighted measure is introduced for each check-sum of the parity-check matrix and a scaling factor is used to weaken the overestimation of extrinsic information. Furthermore, the updating process of the reliability measure takes advantage of turbo-like iterative decoding strategy. The main computational complexity of the proposed algorithm only includes logical and integer operations with the bit uniform quantization criterion. Simulation results show that the novel decoding algorithm can achieve excellent error-correction performance and a fast decoding convergence speed.
Optoelectronics Letters
- Publication Date: Jan. 01, 2018
- Vol. 14, Issue 3, 217 (2018)
A WDM-PON with DPSK modulated downstream and OOK modulated upstream signals based on symmetric 10 Gbit/s wavelength reused bidirectional reflective SOA
El-Nahal Fady I.
We investigate a wavelength-division-multiplexing passive optical network (WDM-PON) with centralized lightwave and direct detection. The system is demonstrated for symmetric 10 Gbit/s differential phase-shift keying (DPSK) downstream signals and on-off keying (OOK) upstream signals, respectively. A wavelength reused scheme is employed to carry the upstream data by using a reflective semiconductor optical amplifier (RSOA) as an intensity modulator at the optical network unit (ONU). The constant-intensity property of the DPSK modulation format can keep high extinction ratio (ER) of downstream signal and reduce the crosstalk to the upstream signal. The bit error rate (BER) performance of our scheme shows that the proposed 10 Gbit/s symmetric WDM-PON can achieve error free transmission over 25-km-long fiber transmission with low power penalty. We investigate a wavelength-division-multiplexing passive optical network (WDM-PON) with centralized lightwave and direct detection. The system is demonstrated for symmetric 10 Gbit/s differential phase-shift keying (DPSK) downstream signals and on-off keying (OOK) upstream signals, respectively. A wavelength reused scheme is employed to carry the upstream data by using a reflective semiconductor optical amplifier (RSOA) as an intensity modulator at the optical network unit (ONU). The constant-intensity property of the DPSK modulation format can keep high extinction ratio (ER) of downstream signal and reduce the crosstalk to the upstream signal. The bit error rate (BER) performance of our scheme shows that the proposed 10 Gbit/s symmetric WDM-PON can achieve error free transmission over 25-km-long fiber transmission with low power penalty.
Optoelectronics Letters
- Publication Date: Jan. 01, 2017
- Vol. 13, Issue 1, 67 (2017)
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