scholarly journals Optical Power Budget of 25+ Gbps IM/DD PON with Digital Signal Post-Equalization

2020 ◽  
Vol 10 (17) ◽  
pp. 6106
Author(s):  
Aleksejs Udalcovs ◽  
Toms Salgals ◽  
Lu Zhang ◽  
Xiaodan Pang ◽  
Anders Djupsjöbacka ◽  
...  
Keyword(s):  
Optical Networks ◽  
Direct Detection ◽  
Optical Power ◽  
Digital Signal ◽  
Single Mode ◽  
Pulse Amplitude ◽  
Power Splitting ◽  
Power Budget ◽  
Sustainable Solutions ◽  
The Impact

While infrastructure providers are expanding their portfolio to offer sustainable solutions for beyond 10 Gbps in the access segment of optical networks, we experimentally compare several modulation format alternatives for future passive optical networks (PONs) aiming to deliver 25+ Gbps net-rates. As promising candidates, we consider the intensity modulation direct detection (IM/DD) schemes such as electrical duobinary (EDB) and 4-level and 8-level pulse amplitude modulations (PAM-4/8). They are more spectrally efficient than the conventional non-return-to-zero on-off-keying (NRZ-OOK) used in current 10G PONs. As we move to higher rates, digital equalization enhances the performance by smoothening the systems imperfection. However, the impact that such equalization has on the optical power budget remains unclear. Therefore, in this article, we fairly compare the optical power budget values of a time division multiplexed PON (TDM-PON) exploiting a linear digital signal equalization at the receiver side. We consider the conventional PON configuration (20 km of single-mode fiber (SMF), 1:N optical power splitting) with IM/DD and net-rates above 25 Gbps. Furthermore, we focus on a downstream transmission imposing the bandwidth limitations of 10G components using a digital filter before the detection. The obtained results show that the use of a digital post-equalization with 43 feed-forward (FF) and 21 feedback (FB) taps can significantly improve the signal quality enabling new alternatives and enhancing the optical power budget.

scholarly journals Low Complexity DSP for High Speed Optical Access Networking

2021 ◽  
Vol 11 (8) ◽  
pp. 3406
Author(s):  
Jinlong Wei ◽  
Cedric Lam ◽  
Ji Zhou ◽  
Ivan Aldaya ◽  
Elias Giacoumidis ◽  
...  
Keyword(s):  
High Speed ◽  
High Performance ◽  
Noise Suppression ◽  
Low Cost ◽  
Optical Power ◽  
Digital Signal ◽  
Single Mode ◽  
Pulse Amplitude ◽  
Power Budget ◽  
Optical Access

A novel low-cost and energy-efficient approach for reaching 40 Gb/s signals is proposed for cost-sensitive optical access networks. Our proposed design is constituted of an innovative low-complex high-performance digital signal processing (DSP) architecture for pulse amplitude modulation (PAM-4), reuses existing commercial cost-effective 10-G components and eliminates the need of a power-hungry radio frequency (RF) component in the transmitter. Using a multi-functional 17-tap reconfigurable adaptive Volterra-based nonlinear equalizer with noise suppression, significant improvement in receiver optical power sensitivity is achieved. Results show that over 30 km of single-mode fiber (SMF) a link power budget of 33 dB is feasible at a bit-error-rate (BER) threshold of 10−3.

scholarly journals Imbalanced Mach-Zehnder Modulator for Fading Suppression in Dispersion-Uncompensated Direct Detection System

Electronics ◽  
2021 ◽  
Vol 10 (22) ◽  
pp. 2866
Author(s):  
Yixiao Zhu ◽  
Xin Miao ◽  
Qi Wu ◽  
Longjie Yin ◽  
Weisheng Hu
Keyword(s):  
Forward Error Correction ◽  
Direct Detection ◽  
Detection System ◽  
Single Mode ◽  
Pulse Amplitude ◽  
Single Mode Fiber ◽  
Error Rates ◽  
Transmission Experiment ◽  
Mach Zehnder Modulator ◽  
The Impact

In this work, we systematically analyze the impact of three kinds of Mach-Zehnder modulator (MZM) imbalances, including bias deviation, amplitude mismatch, and differential time skew in intensity-modulation direct-detection (IM-DD) links. It is shown that, for power fading limited transmission, the imbalances can be utilized as advantages rather than impairments. Specifically, the bias deviation with single-arm driven mode and amplitude mismatch with differential driven mode can increase the available bandwidth by shifting the frequency of fading notches. Meanwhile, time skew provides another way to avoid fading by shaping the double sideband (DSB) signal into a vestigial sideband (VSB) with an asymmetrical transfer function. In the transmission experiment, 34 Gbaud Nyquist 6/8-ary pulse amplitude modulation (PAM-6/8) signals are used for investigation in a 20 km dispersion-uncompensated standard single-mode fiber (SSMF) link. With the help of a Volterra nonlinear equalizer, all three kinds of imbalances can achieve bit-error rates (BERs) below the 7% and 20% hard-decision forward error correction (HD-FEC) thresholds for PAM-6 and PAM-8 signals, respectively. The received power sensitivity is also compared at the back-to-back (BTB) case and after fiber transmission. Both numerical simulation and experimental demonstration confirm that the dispersion-induced power fading can be effectively suppressed with bias, amplitude, or skew imbalance, providing a feasible solution for transmission distance extension of C-band DD links.

scholarly journals DSP-Based 40 GB/s Lane Rate Next-Generation Access Networks

2018 ◽  
Vol 10 (12) ◽  
pp. 118 ◽  
Author(s):  
Jinlong Wei ◽  
Ji Zhou ◽  
Elias Giacoumidis ◽  
Paul Haigh ◽  
Jianming Tang
Keyword(s):  
Optical Networks ◽  
High Speed ◽  
Digital Signal ◽  
Pulse Amplitude ◽  
Network Capacity ◽  
Access Networks ◽  
Next Generation ◽  
Efficient Manner ◽  
Continuous Growth ◽  
Modulation Format

To address the continuous growth in high-speed ubiquitous access required by residential users and enterprises, Telecommunication operators must upgrade their networks to higher data rates. For optical fiber access networks that directly connect end users to metro/regional network, capacity upgrade must be done in a cost- and energy-efficient manner. 40 Gb/s is the possible lane rate for the next generation passive optical networks (NG-PONs). Ideally, existing 10 G PON components could be reused to support 40 Gb/s lane-rate NG-PON transceiver, which requires efficient modulation format and digital signal processing (DSP) to alleviate the bandwidth limitation and fiber dispersion. The major contribution of this work is to offer insight performance comparisons of 40 Gb/s lane rate electrical three level Duobinary, optical Duobinary, and four-level pulse amplitude modulation (PAM-4) for incorporating low complex DSPs, including linear and nonlinear Volterra equalization, as well as maximum likelihood sequence estimation. Detailed analysis and comparison of the complexity of various DSP algorithms are performed. Transceiver bandwidth optimization is also undertaken. The results show that the choices of proper modulation format and DSP configuration depend on the transmission distances of interest.

scholarly journals 137 Gb/s PAM-4 Transmissions at 850 nm over 40 cm Optical Backplane with 25 G Devices with Improved Neural Network-Based Equalization

2019 ◽  
Vol 9 (23) ◽  
pp. 5095
Author(s):  
Qianwu Zhang ◽  
Yuntong Jiang ◽  
Hai Zhou ◽  
Chuanlu Deng ◽  
Shuaihang Duan ◽  
...  
Keyword(s):  
Neural Network ◽  
Forward Error Correction ◽  
Optical Power ◽  
Pulse Amplitude ◽  
Performance Comparison ◽  
Decision Feedback ◽  
Bit Rate ◽  
Optical Backplane ◽  
The Impact ◽  
Equalization Method

An improved neural network-based equalization method is proposed and experimentally demonstrated. The up-to-137 Gb/s transmission of four level pulse amplitude modulation (PAM-4) signals with 25 G class 850 nm optical devices is achieved over an in-house fabricated 40 cm optical backplane. An in-depth investigation is conducted regarding the impact of delayed taps and spans on equalization performance. A performance comparison of the proposed method with the traditional maximum likelihood sequence estimation (MLSE) and decision feedback equalization (DFE) is also undertaken. For the bit rate from 80 to 100 Gb/s, the proposed method achieves an adopted hard-decision forward error correction (HD-FEC) requirement at a received optical power (RoP) of −9 and −8 dBm, while DFE and MLSE cannot meet the HD-FEC requirement. When the bit rate increases from 120 to 137 Gb/s, the proposed equalization method still successfully maintains the acceptable system performance at an RoP of −4 and −2.5 dBm. Furthermore, the specific bit error rate (BER) performances for varied maximum achievable bit rate under different RoPs by applying MLSE and the proposed method are also analyzed. This provides an important potential solution to realize the future data centers.

scholarly journals Programmable Adaptive S-BVTs for Future Optical Metro Networks Adopting SOA-Based Switching Nodes

2018 ◽  
Author(s):  
Laura Martín González ◽  
Sjoerd van der Heide ◽  
Xuwei Xue ◽  
John van Weerdenburg ◽  
Nicola Calabretta ◽  
...  
Keyword(s):  
Optical Networks ◽  
Direct Detection ◽  
Digital Signal ◽  
Cost Effective ◽  
Optical Amplifier ◽  
Limiting Factor ◽  
Bit Rate ◽  
Discrete Multitone ◽  
Key Factor ◽  
Metro Networks

Adaptive Sliceable-Bandwidth Variable Transceivers (S-BVTs) are key enabler for future optical networks. In particular, those based on Discrete MultiTone (DMT) modulation and Direct Detection (DD) can be considered a flexible solution suitable to address the cost efficiency requirement of optical metro networks. In this paper, we propose to use this cost-effective S-BVT option/implementation in optical metro networks adopting switching nodes based on Semiconductor Optical Amplifier (SOA) technology. Bit loading (BL) and power loading (PL) algorithms are applied to the Digital Signal Processing (DSP) modules, to maximize the performance and/or the capacity as well as enhance the flexibility and adaptability of the system. Our analysis considers switching nodes based on SOAs with and without filtering elements and fiber spans of 25 km. We present the results up to 100 km, with and without SOA-based nodes. Firstly, we analyze the adaptive BVT transmission using the Margin Adaptive (MA) BL/PL algorithm at a fixed bit rate of 28 Gb/s. The possibility of controlling the SOAs current is a key factor to face the transmission impairments due to the fiber and the filtering elements. We also analyze the system considering Rate Adaptive (RA) transmission at a fixed target BER of 3.8·10−3, showing that a maximum capacity above 34 Gb/s can be achieved for a single span of 25 km. Although the cascading of filtering elements still constitutes a limiting factor, we show that an improvement of the net bit rate performance can be obtained thanks to the combined use of S-BVT and SOA technology at the switching nodes, resulting in a promising approach for designing future optical metro networks.

scholarly journals A Performance Analysis of a Hybrid OCDMA-PON Configuration Based on IM/DD Fast-OFDM Technique for Access Network

2020 ◽  
Vol 10 (21) ◽  
pp. 7690
Author(s):  
Hichem Mrabet
Keyword(s):  
Wavelength Division Multiplexing ◽  
Orthogonal Frequency Division Multiplexing ◽  
Direct Detection ◽  
Average Power ◽  
Access Network ◽  
Optical Power ◽  
Passive Optical Network ◽  
Free Access ◽  
Power Budget ◽  
Budget Analysis

The purpose of this article is to propose a new configuration based on OCDMA and Fast-OFDM techniques for access network applications. A hybrid intensity modulation with direct detection, fast orthogonal frequency-division multiplexing–code division multiplexing access (IM/DD Fast-OFDM-CDMA) system is analytically and numerically evaluated for an amplifier-free access network. Therefore, system performance is analytically investigated in terms of bit error rate/Q-factor as a function of simultaneous users, fiber length and launched optical power. Firstly, the proposed analytical model includes the overlapping effect among OFDM subcarriers, the peak-to-average power ratio (PAPR), and multiple access interference (MAI). Secondly, a simulation setup is performed, allowing four simultaneous users operating at 40 Gb/s in a passive optical network (PON) context. Furthermore, a power budget analysis is made between IM/DD Fast-OFDM-CDMA, all-optical IM/DD OFDM-CDMA (IM/DD AO-OFDM-CDMA) and OCDMA wavelength division multiplexing (OCDMA-WDM) configurations. It is shown that at 40 Gb/s and by using 2D-hybrid coding (2D-HC), the maximum achievable transmission-reach of IM/DD Fast-OFDM-CDMA is 142 km, which is 34 km and 60 km higher than those provided by the IM/DD AO-OFDM-OCDMA and OCDMA-WDM PON configurations, respectively.

scholarly journals Multi-Twin-SSB Modulation with Direct Detection Based on Kramers–Kronig Scheme for Long-Reach PON Downstream

2019 ◽  
Vol 9 (4) ◽  
pp. 748 ◽  
Author(s):  
Xiang Gao ◽  
Yuancheng Cai ◽  
Bo Xu ◽  
Xiaoling Zhang ◽  
Kun Qiu
Keyword(s):  
Optical Networks ◽  
Forward Error Correction ◽  
Direct Detection ◽  
Chromatic Dispersion ◽  
Optical Network ◽  
Single Mode ◽  
System Optimization ◽  
Single Mode Fiber ◽  
High Data ◽  
Multi Band

As the demand for high data volumes keeps increasing in optical access networks, transmission capacities and distance are becoming bottlenecks for passive optical networks (PONs). To solve this problem, a novel scheme based on multi-twin single sideband (SSB) modulation with direct detection is proposed and investigated in this paper. At the central office, two SSB signals are generated simultaneously with the same digital-to-analog converters (DACs). The twin-SSB signal is not only robust against frequency selected power fading introduced by chromatic dispersion (CD), but also improves the spectral efficiency (SE). By combining a twin-SSB technique with multi-band carrier-less amplitude/phase modulation (multi-CAP), different optical network units (ONUs) can be supported by flexible multi-band allocation based on software-reconfigurable optical transceivers. The Kramers–Kronig (KK) scheme is adopted on the ONU side to effectively mitigate the signal–signal beat interference (SSBI) induced by the square-law detection. The proposed system is extensively studied and validated with four sub-bands using 50 Gbps 16 quadrature amplitude modulation (QAM) modulation for each sub-band using numerical simulations. Digital pre-equalization is introduced at the transmitter-side to balance the performance of different ONUs. After system optimization, a bit error rate (BER) threshold for hard decision forward error correction (HD-FEC) code with 7% redundancy ratio (BER = 3.8 × 10−3) can be reached for all ONUs over 50-km standard single-mode fiber.

scholarly journals 100 Gbaud On–Off Keying/Pulse Amplitude Modulation Links in C-Band for Short-Reach Optical Interconnects

2021 ◽  
Vol 11 (9) ◽  
pp. 4284
Author(s):  
Oskars Ozolins ◽  
Xiaodan Pang ◽  
Aleksejs Udalcovs ◽  
Richard Schatz ◽  
Sandis Spolitis ◽  
...  
Keyword(s):  
Amplitude Modulation ◽  
Optical Interconnects ◽  
High Speed ◽  
Extinction Ratio ◽  
Optical Power ◽  
Single Mode ◽  
Pulse Amplitude ◽  
Single Mode Fiber ◽  
Decision Feedback ◽  
Pulse Amplitude Modulation

We experimentally evaluate the high-speed on–off keying (OOK) and four-level pulse amplitude modulation (PAM4) transmitter’s performance in C-band for short-reach optical interconnects. We demonstrate up to 100 Gbaud OOK and PAM4 transmission over a 400 m standard single-mode fiber with a monolithically integrated externally modulated laser (EML) having 100 GHz 3 dB bandwidth with 2 dB ripple. We evaluate its capabilities to enable 800 GbE client-side links based on eight, and even four, optical lanes for optical interconnect applications. We study the equalizer’s complexity when increasing the baud rate of PAM4 signals. Furthermore, we extend our work with numerical simulations showing the required received optical power (ROP) for a certain bit error rate (BER) for the different combinations of the effective number of bits (ENOB) and extinction ratio (ER) at the transmitter. We also show a possibility to achieve around 1 km dispersion uncompensated transmission with a simple decision feedback equalizer (DFE) for a 100 Gbaud OOK, PAM4, and eight-level PAM (PAM8) link having the received power penalty of around 1 dB.

scholarly journals Photo thermal effect graphene detector featuring 105 Gbit s−1 NRZ and 120 Gbit s−1 PAM4 direct detection

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
S. Marconi ◽  
M. A. Giambra ◽  
A. Montanaro ◽  
V. Mišeikis ◽  
S. Soresi ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
High Speed ◽  
Direct Detection ◽  
Chemical Vapour ◽  
High Mobility ◽  
Optical Power ◽  
Pulse Amplitude ◽  
Thermo Electric ◽  
Available Bandwidth ◽  
Voltage Amplifier

AbstractOne of the main challenges of next generation optical communication is to increase the available bandwidth while reducing the size, cost and power consumption of photonic integrated circuits. Graphene has been recently proposed to be integrated with silicon photonics to meet these goals because of its high mobility, fast carrier dynamics and ultra-broadband optical properties. We focus on graphene photodetectors for high speed datacom and telecom applications based on the photo-thermo-electric effect, allowing for direct optical power to voltage conversion, zero dark current, and ultra-fast operation. We report on a chemical vapour deposition graphene photodetector based on the photo-thermoelectric effect, integrated on a silicon waveguide, providing frequency response >65 GHz and optimized to be interfaced to a 50 Ω voltage amplifier for direct voltage amplification. We demonstrate a system test leading to direct detection of 105 Gbit s−1 non-return to zero and 120 Gbit s−1 4-level pulse amplitude modulation optical signals.

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