This paper proposes a novel wavelength-tuning (λ-tuning) optical line terminal (OLT) protection method for wavelength division multiplexing/time division multiplexing-passive optical networks ...(WDM/TDM-PONs). Since λ-tuning OLT protection achieves redundancy of OLT ports utilizing only the λ-tunability of optical network units (ONUs) that ONUs intrinsically have for colorless operation, no additional equipment such as redundant OLT ports or optical switches is necessary for the protection. The proposed method is based on backup wavelength pre-assignment and a discovery process. Since the backup wavelengths are pre-assigned, the proposed method shortens the service outage time and balances traffic loads among the active OLT ports after OLT protection. Therefore, the proposed method achieves high-level reliability cost-effectively. Through system demonstrations using media access control boards and λ-selective burst-mode transceivers for symmetric 40-Gb/s WDM/TDM-PONs, the validity of the proposal is examined based on the link-up time and throughput measurement for λ-tuning OLT-protection.
We propose and experimentally demonstrate a novel ring-based wavelength-division-multiplexing passive optical network (WDM-PON). By using an orthogonal coding and correlation technique, the ...ring-based WDM-PON can efficiently mitigate the optical beat interference noise induced by Rayleigh backscattering. In our proposed orthogonal coding scheme, no extra light sources are required for the upstream (US) transmission, which means the number of light sources can be halved and the saved wavelengths can be used for more optical network units. In addition, compared to previous ring-based WDM-PONs, the proposed ring-based WDM-PON requires fewer fiber Bragg gratings and no blue/red-band filter, which means the proposed orthogonal coding scheme costs less. The performance of the proposed scheme is investigated through an experiment. In the experiment, 2.5 and 5 Gb/s US data rate and 5 Gb/s downstream data rate are investigated in two different ring architectures. According to the experimental results under different situations, it can be concluded that the US orthogonal coding scheme performs better than the normal US on–off keying in a ring-based WDM-PON. The power margin can be up to 1.8 dB when the US data rate is 2.5 Gb/s, and the power margin can be up to 1.69 dB when the US data rate is 5 Gb/s.
Coherent passive optical network (PON) has been proposed to support the next generation high-speed optical access network owing to the superior receiver sensitivity and thereby the extended power ...budget for 100 G-and-beyond. In addition, PON's flexibility and adaptability are gaining increasing interest. Flexible PON is believed to be a powerful solution in optimizing the overall capacity based on the available channel conditions, i.e., the optical path loss (OPL) and the associated signal-to-noise ratio and nonlinearity impairments of the different groups of optical network units. In this study, we demonstrate the rate-flexible coherent TDM-PON in burst-mode based on probabilistic-shaping (PS) QAM modulations and local oscillator (LO) power adjustment technology, achieving a 300G peak rate and ultra-wide dynamic range. The principle, the burst-mode frame generation as well as the burst-mode signal processing are discussed in detail. To indicate the overall performance of achievable capacity and flexibility, a new metric, namely, dynamic-range and net-rate product ( DRNRP ) is introduced as the indicator to show the optimized throughput. Finally, we experimentally demonstrated a flexible coherent TDM-PON in burst-mode based on 25-GBaud PS-QAMs with the dynamic range of >35-dB in back-to-back. A record DRNRP up to 7,104 dB·Gbps was achieved in the current system with net data rate varying from 255-Gbits/s to 85-Gbits/s as the OPL varies over 20-km fiber transmission.
A 100 Gb/s Intensity Modulated Direct Detection dispersion tolerant downstream PON with 38 dB power budget based on optical duobinary using low-complex equalization is experimentally demonstrated. ...Optical duobinary transmission using avalanche photodiodes in combination with Electrical Duobinary Detection is shown for the first time. This combination is very tolerant to bandwidth limitations at both the transmitter and the receiver. Results are further improved upon by using a wider bandwidth Semiconductor Optical Amplifier -filter- P-type Intrinsic N-type receiver. Optical duobinary transmission also permits transmission at higher optical powers without incurring a meaningful penalty. The results show the promise of using the Optical Duobinary scheme for future very high speed cost-effective PON systems beyond 50 Gb/s.
This paper presents a fast-locking 28 Gbaud PAM-4 CDR targeting for burst-mode operation. By implementing an oversampling scheme tailored for the preamble stage signal according to the pattern ...appearance regulation, the trade-off between the loop bandwidth and the convergence time in the conventional CDR is avoided. In addition, to reduce power consumption in the oversampling mode, a 3-phase sampling scheme equivalent to 3 times-oversampling with a minimal phase shift range of 30<inline-formula> <tex-math notation="LaTeX">^{\circ}</tex-math> </inline-formula> is proposed. The PAM-4 burst-mode CDR also includes a conventional Bang-Bang phase locking loop with a bandwidth of 5 MHz. Realized in a 65nm bulk CMOS technology, the CDR chip achieves 28 Gbaud PAM-4 burst-mode clock recovery within 10 ns. With integrating slicers, phase interpolators and output buffers, the total power consumption of the CDR is 154 mW. Compared with the prior arts, to the best of authors' knowledge, the proposed CDR first achieves on-chip phase-locking with PAM-4 Burst signals, based on the proposed PAM-4 burst-mode signal tailored 3-phase oversampling scheme.
In this Letter, we demonstrate the coexistence of a prototype 200 Gb/s symmetrical coherent point-to-multipoint (PtMP) system with a 50G-PON prototype over 20 km of standard single mode fiber for ...next generation optical access networks. The optical path loss (OPL) of the coherent PtMP prototype exceeds 30.6 dB at 1544 nm in both directions, thus exceeding the N1 OPL class requirements. The prototype also achieve N1 OPL class requirements over the entire C-band. The experiments show a full compatibility between the two systems, which coexistence is enabled by the wavelength plan. We also evaluate the ability of the coherent-PtMP system to support imbalanced terminations in terms of OPLs, to meet the already deployed optical access network requirements. The coherent-PtMP system flexibility is demonstrated through the reconfiguration of its subcarriers to transmit a maximum of 400 Gb/s in a single direction.
In this letter, an enhanced entropy loading discrete multi-tone (EEL-DMT) scheme is proposed for the flexible-rate passive optical network (PON). To achieve a wide range of rate adjustment with fine ...granularity and performance improvements, probabilistic constellation shaping (PCS)-quadrature amplitude modulation (QAM), quadrature phase shift keying (QPSK), and binary phase shift keying (BPSK) are combined in this scheme, and the modulation format of each subcarrier is determined by the allocated entropy. For verifying the feasibility of the proposed scheme, an O-band DMT system is experimentally demonstrated over 20-km standard single-mode fiber (SSMF) transmission using 10G-class directly modulated laser (DML). The experimental results show that the flexible-rate PON based on the EEL-DMT can achieve a wide-range rate adjustment from 12.5 Gb/s to 87.5 Gb/s under the optical power budget from 38 dB to 26 dB, and up to 2-dB receiver sensitivity gain is obtained compared with the adaptive bit and power loading (ABPL)-DMT.
Next-generation mobile networks are expected to incorporate ultra-reliable low latency communication (URLLC). However, the activation and ranging process of Time division multiplexing passive optical ...network (TDM-PON) may provoke conflict to it. In this article, we innovatively use frequency to differentiate joining optical network units (ONUs) and propose a low-latency ONU activation method using delta-sigma modulation (DSM). On the ONU side, the frequency identity, namely electrical tone signal, is converted into binary sequence by DSM, which enables it to be sent directly by optical modules. The registration signal is directly superimposed on the regular upstream (US) burst of the online ONU. Thus, the US traffic does not need to be paused. On the optical line terminal (OLT) side, weak frequency identity information buried in mixed signals can be easily retrieved by coherent detection in the electrical domain with very simple analog devices. Proof of concept experiment results show that the sensitivity of registration signals is −58.3 dBm. When crosstalk ratio = −27dB, the interferometric crosstalk penalty is less than 0.1 dB. After 20 km transmission, the activation requests of different joining ONUs can be detected and distinguished without a quiet window nor degradation on the US traffic.
The relative merits of coherent-enabled optical access network architectures are explored, with a focus on achievable capacity, reach and split ratio. We review the progress in implementing the ...particular case of the ultra dense wavelength division multiplexed (UDWDM) passive optical network (PON), and discuss some challenges and solutions encountered. The applicability of digital signal processing (DSP) to coherent receivers in PONs is shown through the design and implementation of parallelized, low-complexity application-specific digital filters. In this work, we focus on mitigating the impact of local oscillator laser (LO) relative intensity noise (RIN) on receiver sensitivity, and propose an algorithm which compensates for this impairment. This phenomenon is investigated theoretically and then experimentally by evaluating the sensitivity of a coherent receiver incorporating different tunable light sources; a low-RIN external cavity laser (ECL) and a monolithically integrated digital supermode distributed Bragg reflector (DS-DBR) laser. It is shown that the RIN of the signal laser does not significantly contribute to the degradation of the receiver sensitivity. Finally, a 10 Gbit/s coherent PON is demonstrated using a DS-DBR laser as the LO laser. It is found that a receiver sensitivity of -38.8 dBm is achievable assuming the use of hard-decision forward error correction.
This paper proposes a novel method for N∶1 optical line terminal (OLT) protection on wavelengthdivision- multiplexing/time-division-multiplexing passive optical networks (WDM/TDM-PONs). The N∶1 OLT ...protection scheme based on in-service wavelength tuning -tuning) at optical network units (ONUs) provides reliable and cost-effective protection without the need for equipment specific to OLT protection on either the ONU or OLT side. Since the normal multipoint control protocol (MPCP) and backup wavelength pre-assignment are utilized, the proposed method significantly shortens the maximum protection time in N∶1 OLT protection. Results of trials on a 40 Gbit/s (10 Gbit∕s × 4 wavelengths) system with 40 km single mode fiber (SMF) transmission show service interruption times of less than 50 ms at all times, even with the practical -tuning time of 30 ms. The system trials also verify that the proposed method assures service interruption times of less than 50 ms, even with the split ratio on a PON of up to 512. These results verify that the proposed method is promising for next-generation multiservice convergence access networks.
