Wavelength Division Multiplexed Passive Optical Network System Research Articles

Enhanced PON and AMCC Joint Transmission with GMM-Based Probability Shaping Techniques

In ITU-T standards, auxiliary management and control channels (AMCCs), as defined, facilitate the rapid deployment and efficient management of wavelength division multiplexing passive optical network (WDM-PON) systems. The super-imposition of an AMCC introduces additional interference to a PON signal, resulting in the degradation of the performance of the overall transmission. In prior research, we proposed employing a Gaussian mixture model (GMM) to fit a baseband-modulated AMCC signal. Following the analysis of the interference model and the distribution characteristics of received signal errors, we propose a combined optimization method for a transmitter and receiver in this paper. This method, grounded in probabilistic shaping (PS) techniques, optimizes the probability distribution of the transmitted signal based on the AMCC interference model, with the objective of reducing the error rate in PON signal transmission. We have validated this approach within a 50G-PON experimental system by utilizing PAM4 modulation. The experimental results demonstrate the effectiveness of this method for mitigating the impact of baseband-modulated AMCC, thereby reducing the error rate in PON signal transmission. The approach presented in this paper can further minimize the performance degradation introduced by baseband-modulated AMCC in WDM-PON systems, enhancing the efficiency of WDM-PON deployment.

Next-generation WDM-PON optimized architecture for FTTH network with maximal resources for high throughput

Abstract To achieve high data rate, futuristic wavelength division multiplexing passive optical network (WDM-PON) has pursued due to capability of multiplexing individual wavelength. This paper illustrates the possibility of different data rates along with distance to solve the challenges for next-generation WDM-PON systems. It is superior to present PON design due to rapid progress in different passive components for access network. In this paper, recent progress such as 20 Gb/s (gigabits per second) to 80 Gbps. WDM-PON technology has been carried out. Due to recent development in PON systems, demonstration of 80 Gbps (10 Gbps per wavelength * 8) based WDM-PON system with simplified and optimized design for last mile is presented. The simulation results have been compared to demonstrate the effect of the results achieved. At last, better quality (Q)-factor of 3.46, low value of BER (bit error rate) i.e., 2.48 × 10−11 with reach of 80 km whereas high value of Q-factor of 22.16, eye height of 4.75 and BER of 3.61 × 10−10 has achieved successfully using WDM-PON system.

Hybrid Self-Protected Fiber-FSO WDM-PON System with Fiber Breakage Prevention

In this research, we present and design a blended wavelength-division-multiplexing passive optical network (WDM-PON) architecture to deliver both baseband and free-space optical (FSO) signals by using two wavelength bands over an available bandwidth to avoid the signal interference. Only using few additional components in the optical line termination (OLT) and optical network unit (ONU)/optical wireless unit (OWU) can achieve self-protected operation in the presented hybrid fiber-FSO access network against fiber breakage. In the measurement, eight WDM wavelengths with 24.3 Gbit/s on-off keying (OOK) modulation format are applied to verify and discuss the bit error rate (BER) performances of baseband and FSO signals, respectively, through 25 km fiber and 2 m wireless FSO connections. Therefore, the presented PON not only can deliver both baseband and FSO traffics, but can also provide a self-restored mechanism against fiber fault.

Protection Scheme for a Wavelength-Division-Multiplexed Passive Optical Network Based on Reconfigurable Optical Amplifiers

This paper demonstrates a wavelength-division-multiplexed passive optical network (WDM-PON) scheme based on novel reconfigurable optical amplifiers (ROAs). The measured switching characteristics of the ROA3 constructed with a 2 × 2 crossbar optical switch and a four-port reversible optical circulator (OC) and a conventional EDFA can meet the requirements of most network management and surveillance. The self-made four-port reversible OC’s response time is less than 2 ms, and its insertion losses are about 1 dB or less for all the transmission paths and switching states. An optimal design of ROAs is proposed and evaluated for bidirectional optical amplifier protection, in which ROA3 has an EDF length of 7.5 m long with a 1480 nm pump laser and possesses a backward or forward pumping configuration with the corresponding pump power of 200 mW or 50 mW. We verified the scheme’s feasibility through a simulation of WDM-PON systems with 40 downstream and upstream channels. This scheme enables the intelligent protection switching in practical operation scenarios for high-capacity multi-wavelength networks.

WDM-PON Management and Control by Auxiliary Management and Control Channel for 5G Mobile Fronthaul

The demand for fifth generation (5G) mobile systems has been exploding. There are strict latency and transmission capacity requirements, especially in the optical fiber section called the mobile fronthaul. A wavelength division multiplexing passive optical network (WDM-PON) system is an attractive solution to accommodate the high demand of traffic. However, wavelength management, which is important in a WDM-PON system, has not been sufficiently studied at the system level. In previous studies, control by a management control channel independent of the client signal, called the auxiliary management and control channel (AMCC), has been considered in many cases. In most of these studies, physical layer evaluation, such as the effect of superimposing the management control channel, was conducted for feasibility studies, and it was only confirmed that the effect was minor by measuring the bit error rate. In this paper, we review and compare the superimposition schemes of the AMCC to clarify operating conditions such as modulation format and modulation index of the AMCC signals. In addition, we propose a WDM-PON system managed using AMCC for ONU activation, wavelength adjustment and alive monitoring. We then discuss the connection of a WDM-PON prototype system we developed to a 5G mobile system to evaluate the effect of throughput on user equipment. The results indicate that the WDM-PON prototype system did not degrade (less than 2%) the downlink throughput even when the wavelength adjustment function was used against wavelength drift.

Wavelength division multiplexing-passive optical network using a graphene-based ultrashort pulsed fiber laser

We present a wavelength division multiplexing-passive optical network (WDM-PON) that uses a graphene-based ultrashort pulsed fiber laser (USPL) as multi-wavelength source. The performance of this WDM-PON system is analyzed in two stages: at first, the USPL was designed, implemented, and characterized experimentally. Then experimental data from the USPL spectrum were then introduced into a simulated network using the software VPItransmissionMaker™, for testing the WDM-PON system performance. The results show that it is possible to achieve an error-free transmission (BER < 10 − 9) for distances up to 30 km using a non-return to zero modulation format with a bit rate of 10 Gbps and 18 dB optical signal-to-noise ratio (OSNR). In comparison with an externally modulated distributed-feedback laser, a distance and OSNR penalties < 5 km and 0.4 dB, respectively, were achieved. Furthermore, this USPL exhibited a 3-dB bandwidth close to 22 nm, which means more than 100 optical channels could be obtained when considering a 12.5 GHz standard grid. Thus due to the number of generated channels, a remarkable cost reduction could be achieved in comparison with conventional WDM-PON systems.

40 Gb/s wavelength division multiplexing-passive optical network (WDM-PON) for undersea wireless optical communication

Abstract We demonstrate the design and simulation of a long range four-channel wavelength division multiplexing-passive optical network (WDM-PON) operating at 40 Gb/s (4 × 10 Gb/s) in downstream transmission for undersea wireless optical communication. The proposed model consists of two separate subsections between the optical transmitter and receiver. The first subsection consists of the central office and 50 km long feeder fiber for transmitting the optical signal from a distant base station to the 1 × 4 optical demultiplexer located at the sea shore. The second subsection comprises 500 m distributed fiber from the 1 × 4 optical demultiplexer to the terminal point placed at the bottom of the sea and 15–20 m optical wireless channel inside sea water. Simulation results confirmed successful transmission of optical signals from the 50 km distant optical transmitter to the optical receiver located maximum 15 m inside the sea water with a signal-to-noise ratio of ∼20.96 dB, bit error rate of ∼1.55 × 10−8, and quality factor of ∼5.584. The eye diagram at the receiving end also exemplifies quality downstream data transmission at a rate of 10 Gb/s per channel. In addition, we compare the simulation results of the four-channel 40 Gb/s WDM-PON system with a four-channel WDM-PON system operating at 4 Gb/s (4 × 1 Gb/s). Simulation results confirm maximum reach of 17.5 m inside sea water at a cost of significant reduction in data rate. Furthermore, we analyze the system availability of the proposed WDM-PONs and find convincing results for high-speed secured data transmission under water.

Symmetry 28 Gbps/λ WDM Access Network Together With Confidential Connection Between Two Specific Clients

In this work, we demonstrate a symmetry 28 Gbps/ $\lambda $ on-off keying (OOK) wavelength-division-multiplexing passive optical network (WDM-PON) architecture together with confidential connection between two specific optical network units (ONUs). The presented PON access network also can prevent the Rayleigh backscattering (RB) induced interference noise. Here, to avoid re-deployment of optical fiber and increase cost, a ring-based fiber connection is proposed to connect each ONU for personal information link, when the data connection between two ONUs can be changed arbitrarily. Moreover, the corresponding signal performances of the presented WDM-PON system are also studied and discussed.

LDPC-Coded Probabilistic Shaping PAM8 Employing a Novel Bit-Weighted Distribution Matching in WDM-PON

We propose and experimentally demonstrate a wavelength-division-multiplexing passive optical network (WDM-PON) employing low-density parity-check (LDPC) coded probabilistic shaping 8-level pulse amplitude modulation (PS-PAM8). In such a splitter-based WDM-PON system with direct detection, a novel probabilistic shaping (PS) method based on a bit-weighted distribution matching (BWDM) for near-Gaussian distribution (NGD) is proposed for the first time. For typical PS schemes based on typical arithmetic distribution matching (ADM) and constant composition distribution matching (CCDM), refining intervals continuously is needed to find the target symbol probability, which will necessarily introduce a plenty of additional redundant bits in the process of the target symbol probability distribution (SPD) emulation from data source. Different from ADM and CCDM, the PS scheme based on BWDM is realized by a simple bit-weight intervention algorithm with low hardware and calculation complexity, which only includes weight-marking bit insertion and bit inversion processes for adjustable SPD kurtosis. The experimental results show that by employing the proposed PS-PAM8, the receiver power sensitivity and system fiber nonlinear effect tolerance can be dramatically improved compared with the unshaped signal. Thus, the WDM-PON employing PS-PAM8 is of cost-effective advantage, which can serve more available optical network units due to the enlarged system loss budget for the optical distribution network.

Research on Power Optimization Based on Adaptive Passive Optical Networks

Abstract For the commercial wavelength division multiplexing passive optical network (WDM-PON) with standard single-mode fiber SSMF-28 and 1:64 passive fiber branching at its far end (RN) and 100 GHz C-band continuous wavelength (CW) lasers, the maximum coverage and optimal transmission power of STM-16 and STM-64 with external modulators at different speeds and wave numbers (4λ, 8λ and 16λ) are obtained, respectively. The performance parameter of the high data rate WDM-PON system is analyzed with respect to a number of channels and reach. In order to improve the network utilization and receiving efficiency, the influence of different channels and transmission distances on the performance of high data rate WDM-PON system is analyzed. Simulation analysis with Optisystem15.0. The maximum transmission power required to achieve the maximum transmission distance under the condition of nonlinear constraints is obtained. In order to save power consumption, the configuration of each multi-band PON is optimized in terms of transmission power. It is found that WDM-PON system has to compromise between aggregated data rate and system reach. Future software defined access network reconfigure the access network depending on the dynamic demand and the resources available. Hence depending on the distance between the optical line terminal (OLT) and optical network unit (ONU) guaranteed data rate can be estimated. ONU is equipped with a tunable optical filter (TOF) hence future wavelength can be reconfigured by both service provider and user. It makes it possible for software to customize optical access network.

LDPC-coded Probabilistic Shaping PAM4 Based on Many-to-One Mapping in WDM-PON

In this article, a 5 × 25-GBaud wavelength division multiplexing passive optical network (WDM-PON) is reported and experimentally demonstrated with each channel carrying a low-density parity check- (LDPC-) coded probabilistic shaping 4-ary pulse amplitude modulated signal (PS-PAM4). In such a splitter-based WDM-PON system, 8-point 3-bits/symbol PAM8 is mapped into 4-point PAM4 by adoption of a many-to-one mapping scheme, which enables improved receiver power sensitivity and increased spectral efficiency, compared with the uniformly-distributed PAM4. Different from the typical constant composition distribution matching method for PS, no shaping codes or PS overheads are needed in our PS-PAM4 signal which is to be encoded and decoded in a LDPC-based bit-interleaved coded modulation iterative decoding (BICM-ID) system for the compatibility with the forward error correction (FEC) applied in most of the optical transponders currently. In the BICM-ID system, the extrinsic messages are delivered circularly between the PS de-mapper and the LDPC decoder to deal with PS many-to-one mapping ambiguity. The experimental results strive to make the WDM-PON system better spectrum efficiency, as well as superior receiver power sensitivity and fiber nonlinear effect tolerance, thus maximizing the input power at the optical line terminal and economic efficiency of the system due to ampler loss budget provided for the legacy optical distribution networks.

Cost effective OLT arrangements in 40 Gbps WDM-PON using AWG with a single laser

In this paper, we upgraded the optical line terminal (OLT) of the optical access network for 40 Gbps by proposing a cost effective OLT based on cascaded model of phase modulator and arrayed waveguide grating for wavelength division multiplexed passive optical network (WDM-PON). The conventional setup at OLT side of WDM-PON system is replaced with a new arrangement containing single laser source in cascade with phase modulator and AWG, whereas the phase modulator is tailored with RF source. The phase modulator generates multicarrier signal and AWG splits the signal into multiple single wavelengths based on its routing configurations. AWG is actually used as a passing band periodical filter that routs the input wavelengths to four outputs depending on its free spectral range. Across each routed wavelength, differential phase shift keying is used in downlink transmission for 10 Gbps, while intensity modulation is employed in the uplink transmission based on off-keying. 40 Gbps full duplex transmission via 20 km fibre span is successfully achieved with minimum power loss and effective results. Transmission performances are examined with negligible power penalties, better Q-factors, handsome eye openings and good eye heights, which confirm the deployment of proposed arrangement in the next generation access network.

Hardware-Efficient Signal Processing Technologies for Coherent PON Systems

Future passive optical network (PON) systems supporting more than 50 Gb/s/λ present a challenge for the use of intensity modulation direct detection (IM-DD). Since coherent technology improves the receiver sensitivity over that of IM-DD, it is a promising candidate for 100 Gb/s or higher PON systems. Introducing hardware-efficient signal processing technologies tailored to PON systems will help render coherent technology suitable for PON systems. We here review hardware-efficient signal processing technologies suitable for PON systems. We introduce two types of simplified adaptive equalization (AEQ), one which sacrifices differential group delay compensation (DGDC), and another which sacrifices some chromatic dispersion compensation but does provide DGDC. Transmission experiments on a 100 Gb/s/λ-based coherent wavelength division multiplexing (WDM) PON system showed that simplified AEQ without DGDC and with DGDC exhibited only 0.2 and 1.4 dB penalty, respectively, compared with conventional DSP. The additional penalty due to the maximum possible cumulative DGD was evaluated by numerical simulation. Conventional AEQ and the simplified AEQ with DGDC showed negligible penalty, but the simplified AEQ without DGDC showed a 1.4 dB penalty. We also introduce simplified carrier phase recovery (CPR) with interpolarization phase offset estimation, and this showed the same performance as the conventional DSP, in both experiment and simulation. Taking these results into account, 100 Gb/s/λ-based coherent WDM PON systems with the simplified AEQs in combination with the simplified CPR were shown to be able to support the loss budget required for eight ONU splits over an 80 km span of single mode fiber.

THEORETICAL ANALYSIS OF SINGLE-FIBER TRANSMISSION OVER WDM-PON SYSTEMS

In this paper, a rigorous theoretical analysis on optical beat interferometric (OBI) noises caused by the Rayleigh backscattering (RB) and Fresnel reflection (FR) effects on the performance of a single-fiber single-wavelength WDM-PON (wavelength division multiplexing-passive optical network) transmission system has been presented. Two categories of PON are evaluated: a conventional and a long-reach WDM-PON system. The conventional WDM-PON took place in an access network for a typical transmission distance of 20 km without any optical amplification at the remote node (RN). In this case, the gain of the optimal reflective optical network unit (ONU) will depend on the relative RB power and also the FRs magnitudes and locations along the optical fiber channel/transmission link. However, in the cases of the long-reach WDM-PON deployed at a transmission distance of 100 km or further, the optical amplifiers are indispensable to enhance the optical power budget and to prevent the effect of fiber nonlinearities that may occur at high power injection levels. Although the presence of an optical amplifier (OA) in a long-reach WDM-PON will actually give some additional gain to the whole system, as a result it also produces the worse RB and FR effects to the system itself. A crosstalk to signal (C/S) ratio is used as a key performance indicator of whether the transmission system is in good working order or not. Therefore, this study may provide insight and relevant information in terms of transmission optimization for WDM-PON systems and developments in the future. To educate on the current technologies and developments surrounding conventional and long-reach WDM-PON, a brief overview is provided in the background part of the introduction.

Flattened Optical Multicarrier Generation Technique for Optical Line Terminal Side in Next Generation WDM-PON Supporting High Data Rate Transmission

A novel and cost effective optical multicarrier (OMC) generator is introduced in this article. OMC is generated by connecting three modulators in cascade with laser source, where laser is connected with one amplitude modulator and two Mach-Zehnder modulators (MZMs) in cascade. The amplitude modulator is used for the first time in cascade configurations for the generation of OMC signal. All the modulators are driven by RF signal of 30 GHz where specially tailored or fiber-Bragg gratings are not required. The generated OMC is very flat due to the proper DC biasing of MZMs and being related to the optimum ratio of DC bias and half wave voltage of MZMs. OMC offers 61 comb lines with minimum excursions in its comb lines, having tone-to-noise ratio greater than 40 dB, frequency spacing equal to 30 GHz, and high side mode suppression ratio over 35 dB. In this configuration, no optical phase shifter, amplifier, or attenuator is used. Second, optical line terminal (OLT) costs of conventional wavelength division multiplexed passive optical network (WDM-PON) system are reduced by introducing the proposed OMC source at OLT side of WDM-PON system for large capacity WDM-PON that supports numerous users. At OLT side, each out of 61 carriers is capable of supporting 10 Gb/s differential phase shift keying based data in downlink transmission. In the uplink transmission, half power splitters are deployed at optical network unit (ONU) side, where half power of the downlink signal is utilized for uplink transmission based on intensity-modulated on-offkeying resulting in colorless ONUs. The detailed power budget is discussed for the validity of results. Bit error rate (BER), eye patterns, and power penalties lie in the metrics encountered for the analysis in full duplex PON’s transmission. Minimum power penalties at specific BERs of different channels show the applicability of the proposed model.

Demonstration of 100-Gb/s/λ-Based Coherent WDM-PON System Using New AGC EDFA Based Upstream Preamplifier and Optically Superimposed AMCC Function

In this paper, we present the first 100-Gb/s/λ-based coherent wavelength division multiplexing passive optical network (WDM-PON) prototype system, highlighting a real-time 100-Gb/s coherent transceiver with a simplified digital signal processing suitable for access spans, and a new automatic-gain-controlled erbium-doped fiber amplifier based preamplifier with an amplified spontaneous emission compensation function for the upstream to improve the minimum receiver sensitivity for coherent detection, especially at very low received signal power. Thanks to our proposed technologies, this first demonstration achieved an increased bidirectional loss budget of more than 39.1 dB, which supports 80 km transmission with eight optical network unit splits, with an improved upstream receiver sensitivity of -38.1 dBm. In addition, to show the feasibility of the proposed 100-Gb/s/ λ-based coherent WDM-PON as a promising candidate for forthcoming 5G mobile fronthaul networks, we further investigate experimentally a 128-kb/s auxiliary management and control channel (AMCC) superimposed on the 100-Gb/s dual polarization quadrature phase-shift keying (DP-QPSK) signals employed by the 100-Gb/s/λ -based coherent WDM-PON system. By setting the modulation index of the AMCC signals between 5% and 40%, we also successfully demonstrated 100-Gb/s DP-QPSK signal transmission with only a small power penalty of 0.2 dB due to the introduction of the AMCC signal.

Colorless WDM-PON using single side band carrier suppressed signals mitigating carrier rayleigh backscattering

A new scheme is offered for minimizing carrier Rayleigh backscattering (CRB) in single feeder fiber based wavelength division multiplexed passive optical network (WDM-PON). The proposed scheme is based on single side band carrier suppressed (SSB-CS)signal, both at network and receiver sides, used for the first time at optical line terminal (OLT) and optical network unit (ONU)sides. We use dual-drive Mach-zehnder modulator (DD-MZM)for generating SSB-CS signals, which decreased the expense per bit in full transmission. SSB-S mitigated CRB, both at OLT and ONU sides, because of having no chance of reflections from the carrier. Since no extra dedicated RF or laser source is used at ONU side, we thus achieve cost effective colorless WDM-PON system. Suppressed signals from four channels, each of 10 Gbps, are multiplexed before injecting into the fiber span of 25 km at OLT. At ONU side, half of the down-link power is used for re-modulating the data signal. The simulation results show an error free transmission. Moreover, the detailed power budget calculations show that the proposed scheme can be sought out for splitting ratio up to 128. Hence it offers enough system's margin for unseen losses.

Pulsed laser-based optical frequency comb generator for high capacity wavelength division multiplexed passive optical network supporting 1.2 Tbps

An architecture for flattened and broad spectrum multicarriers is presented by generating 60 comb lines from pulsed laser driven by user-defined bit stream in cascade with three modulators. The proposed scheme is a cost-effective architecture for optical line terminal (OLT) in wavelength division multiplexed passive optical network (WDM-PON) system. The optical frequency comb generator consists of a pulsed laser in cascade with a phase modulator and two Mach–Zehnder modulators driven by an RF source incorporating no phase shifter, filter, or electrical amplifier. Optical frequency comb generation is deployed in the simulation environment at OLT in WDM-PON system supports 1.2-Tbps data rate. With 10-GHz frequency spacing, each frequency tone carries data signal of 20 Gbps-based differential quadrature phase shift keying (DQPSK) in downlink transmission. We adopt DQPSK-based modulation technique in the downlink transmission because it supports 2 bits per symbol, which increases the data rate in WDM-PON system. Furthermore, DQPSK format is tolerant to different types of dispersions and has a high spectral efficiency with less complex configurations. Part of the downlink power is utilized in the uplink transmission; the uplink transmission is based on intensity modulated on-off keying. Minimum power penalties have been observed with excellent eye diagrams and other transmission performances at specified bit error rates.

Multiwavelength Laser Module Based on Distribute Feedback Laser Diode for Broadcast and Communication Systems

In this paper, we proposed a cost-effective broadcast signal transmission scheme using a distributed feedback laser diode (DFB-LD) for wavelength-division-multiplexing passive optical network (WDM-PON) systems. The DFB-LD is directly modulated with a single-tone radio frequency signal to generate multiple optical carriers. An optical signal-to-noise ratio (OSNR) is enhanced using a delay interferometer as a double-pass interferometer. Orthogonal frequency division multiplexing (OFDM) and on-off keying (OOK) signals are experimentally demonstrated to test the broadcasting scheme. We measured the bit-error-rate (BER) and the power penalty after the broadcasting OFDM and OOK signals are transmitted through a 25-km single-mode fiber. An excellent performance of BER is achieved for both OOK and OFDM signals. The proposed scheme is a practical and cost-effective solution for broadcast signal transmissions in WDM-PON systems.

Optical frequency comb generation with high tone-to-noise ratio for large-capacity wavelength division multiplexed passive optical network

We propose a technique for the generation of optical frequency comb from a single source, which reduces the costs of optical access networks. Two Mach-Zehnder modulators are cascaded with one phase modulator driven by radiofrequency signals. With 10-GHz frequency spacing, the generated 40 optical multicarriers have good tone-to-noise ratio with least excursions in their comb lines. The laser array at the optical line terminal of the conventional wavelength division multiplexed passive optical network (WDM-PON) system has been replaced with optical frequency comb generator (OFCG), which may result in cost-effective optical line terminal (OLT) supporting a large-capacity WDM-PON system. Of 40 carriers generated, each carrier carries 10 Gbps data based on differential phase-shift keying. Four hundred Gbps multiplexed data from all channels are successfully transmitted through a fiber span of 25 km with negligible power penalties. Part of the downlink signal is used in uplink transmission at optical network unit where intensity-modulated on-off keying is deployed for remodulation. Theoretical analysis of the proposed WDM-PON system based on OFCG are in good agreement with simulation results. The metrics considered for the analysis of the proposed OFCG in a WDM-PON system are power penalties of the full-duplex transmission, eye diagrams, and bit error rate.