Wavelength Division Multiplexing Passive Optical Network Research Articles

Design and Evaluation of Elastic Optical Access Network Based on WDM-PON and OFDM Technology

The elastic optical network is a novel idea that is targeted at realizing flexible bandwidth allocation according to diverse traffic needs and requirements. Meanwhile, with the increasing demand of data rates in optical access networks, it is urgent to upgrade the current passive optical networks (PONs) through more elastic approaches. In this paper, we propose a kind of elastic optical access network based on wavelength-division multiplexing PON (WDM-PON) and orthogonal frequency-division multiplexing (OFDM) technology, in which finer bandwidth allocation granularity and a flexible wavelength switch are realized. We simulate the transmission performance of the system in both uplinks and downlinks.We also evaluate the elasticity of the system and propose an improved dynamic bandwidth allocation algorithm that has been shown to be the most effective in reducing the blocking rate and bandwidth fragmentation.

Wavelength Sharing and Reuse in Dual-Band WDM-PON Systems Employing WRC-FPLDs

In this letter, for the first time, we propose a dual-band wavelength division multiplexed passive optical network (WDM-PON) architecture that enables efficient nonoverlapping wavelength reuse and mitigates bidirectional transmission impairments. Weak-resonant-cavity Fabry-Perot laser diodes (WRC-FPLDs) with gain spectra across $C$ -band and $L$ -band are implemented to achieve desirable colorless, uncooled, and inexpensive optical network units. The side mode suppression ratio and modulation performance of the injection-locked WRC-FPLDs with operational wavelengths from 1550 to 1580 nm are studied. The 25-km transmission experiments have been demonstrated, where the injection-locked WRC-FPLDs are directly modulated with up to 5-Gb/s on-off-keying (OOK) upstream signals. Improved signal quality with bit-error rates $ is obtained which confirms that the dual-band architecture with wavelength sharing can be a potential candidate for future WDM-PON deployments.

Fault location for WDM‐PON using a multiple‐longitudinal‐mode laser modulated by chaotic wave

ABSTRACTWe experimentally demonstrate a cost‐effective method to locate faults in wavelength‐division‐multiplexing passive optical network (WDM‐PON) utilizing a multiple‐longitudinal‐mode Fabry–Perot semiconductor laser directly modulated by chaotic wave from a Colpitts oscillator. Due to chaos modulation, every longitudinal mode of the laser has chaotic intensity waveform. Using a tunable optical filter selects a mode to detect the wavelength‐matched branch of WDM‐PON using chaos correlation technique. Experimental results show that the unterminated fiber end, mismatch connector and fiber breakpoint can be preciously located. A detection range of approximately 75 km and a range‐independent spatial resolution of 14 cm are achieved. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2502–2506, 2015

WDM PONs based on colorless technology

Wavelength Division Multiplexing (WDM) Passive Optical Network (PON) is foreseen to be part of the Next Generation Passive Optical Networks. Business and mobile fronthaul networks already express the need to develop WDM PONs in the access segment. Fixed wavelength transceivers based on Coarse WDM are already available to respond to today’s market needs but Dense WDM technologies will be needed and colorless technologies are essential to provide simple and cost-effective WDM PON systems. We propose in this paper to demonstrate the capabilities of a DWDM PON system prototype based on self-seeded RSOAs and designed to transmit CPRI over 60km of fiber at 2.5Gbit/s.

Polarization multiplexing of two MIMO RoF signals and one baseband signal over a single wavelength

Next-generation (NG) access networks require simultaneous provision of wired and wireless services and high data rates to meet the large demands of mobility and multiple services. In this paper, we propose a novel spectral efficient radio over fiber (RoF) scheme to simultaneously provide two spatially multiplexed multiple input multiple output (MIMO) wireless signals with a baseband (BB) wired signal in one wavelength using a centralized light source. The proposed scheme can be applicable to wavelength division multiplexed passive optical networks (WDM-PONs). The BB signal is modulated at a low extinction ratio (ER). The modulated light is re-used to modulate two MIMO signals that have the same carrier frequency that is combined optically using polarization-division-multiplexing (PDM). The data rate for each MIMO stream was 1.25Gb/s, and the data rate was 2.5Gb/s for the BB signal. Error free performance with a bit error rate (BER) of 10−9 was achieved for all three signals after 20km and 60km through single mode fiber (SMF) for 16-QAM and 4-QAM for the MIMO signals, respectively.

Bidirectional 40 Gb/s/λ, 100 km-reach, channel-reuse WDM-PON employing tunable optical transceiver with optical intensity detection-based wavelength management

We experimentally demonstrate a channel-reuse, bidirectional 40Gb/s/λ, long-reach wavelength-division-multiplexing passive optical network (WDM-PON) and an optical intensity detection-based wavelength management method for tunable optical transceiver used in colorless optical network unit. A 100km reach, channel-reuse, 40Gb/s/λ transmission on a 100GHz WDM grid is achieved. Transmission performance is also measured with different optical-signal-to-Rayleigh-backscattering-noise ratios (OSRBNRs) and different central wavelength shifts (WSs) between upstream signal and downstream signal in the channel-reuse system. Optimal operating wavelength for the uplink optical signal and effective OSRBNR configurations taking into account AWG pass-band, wavelength instability of the bidirectional optical transmitters are proposed.

Fabrication of Low-Cost Multiwavelength Laser Arrays for OLTs in WDM-PONs by Combining the SAG and BIG Techniques

We present the fabrication of a low-cost multiwavelength laser array monolithically integrated with a passive optical combiner for optical line terminals (OLTs) in wavelength-division multiplexing (WDM) passive optical networks (PONs). By combining the upper separate confinement heterostructure layer selective area growth technique and the bundle integrated guide technique, both multiwavelength emission with highly uniform spacing and low-loss passive-waveguide material can be obtained in a single metal–organic chemical vapor deposition (MOCVD) growth step, which greatly simplifies the fabrication of the device. A prototype laser array, which has four distributed feedback (DFB) laser elements and a multimode interference coupler as combiner, is successfully fabricated. The shallow ridge structure of the DFB lasers and the deep ridge structure of the passive waveguides are obtained by a single dry etching step, which further eases the device fabrication. The properties of the device are measured and discussed. The results indicate that our method is promising for fabricating cost-effective OLT light sources for WDM-PONs.

In-band simultaneous transmission of baseband and broadcast signals in wavelength reused bidirectional passive optical network

Reflective semiconductor optical amplifier (RSOA) based bidirectional wavelength division multiplexing passive optical network (WDM-PON) is proposed and analyzed for broadcasting services along with conventional baseband signal. The downstream baseband signal is spectrally shaped for in-band transmission of broadcast signal, which ensures effective utilization of transmission bandwidth. The modulated downstream optical signal is further reused for upstream data modulation and transmitted over the same fiber with suppressed re-modulation and rayleigh backscattering noises. The proposed WDM-PON is successfully demonstrated for 10Gb/s downstream baseband signal, 100Mb/s 16-QAM (quadrature amplitude modulation) in-band broadcast signal and wavelength reused 1.25Gb/s upstream signal. Error free operation for both the baseband signals as well as low value of error vector magnitude (EVM) for broadcast data are simultaneously achieved in acceptable receiver sensitivity.

Increment of Access Points in Integrated System of Wavelength Division Multiplexed Passive Optical Network Radio over Fiber.

This paper describes a novel technique to increase the numbers of access points (APs) in a wavelength division multiplexed-passive optical network (WDM-PON) integrated in a 100 GHz radio-over-fiber (RoF). Eight multi-carriers separated by 25 GHz intervals were generated in the range of 193.025 to 193.200 THz using a microring resonator (MRR) system incorporating an add-drop filter system. All optically generated multi-carriers were utilized in an integrated system of WDM-PON-RoF for transmission of four 43.6 Gb/sec orthogonal frequency division multiplexing (OFDM) signals. Results showed that an acceptable BER variation for different path lengths up to 25 km was achievable for all four access points and thus the transmission of four OFDM channels is feasible for a 25 km standard single mode fiber (SSMF) path length.

Multi-service RoF links with colorless upstream transmission based on orthogonal phase-correlated modulation.

We propose and experimentally demonstrate a full-duplex radio-over-fiber (RoF) system with colorless upstream transmission based on orthogonal phase-correlated modulation (OPM). This new OPM scheme, which realized by a polarization rotator (PR) and a single-driver Mach-Zahnder modulator (MZM) at the central office (CO), achieves polarization-orthogonality between the optical carrier (OC) and subcarriers generated by radio frequency (RF) signals. By adjusting a polarization controller (PC) in the remote access units (RAU), different modulation schemes can be flexibly implemented, e.g. double-sideband (DSB) modulation for low RF service and optical carrier suppression (OCS) modulation for millimeter-wave (mm-wave) service. In the meantime, the OC can be reused for the upstream transmission without any filtering and additional PC. A proof-of-concept experiment is conducted to demonstrate the feasibility of proposed scheme, where downstream 800-Mb/s orthogonal frequency division multiplexing (OFDM) signal at 58 GHz as an mm-wave service and 800-Mb/s OFDM signal at 0.3 GHz as a low frequency wireless service, as well as an upstream 1-Gb/s on-off keying (OOK) are simultaneously delivered in a shared architecture. By providing heterogeneous services and colorless upstream transmission, the proposed architecture can be seamlessly integrated in wavelength division multiplexing passive optical network (WDM-PON).

25-GHz Spaced Spectrum-Sliced WDM PON Using 50-GHz AWGs

We demonstrate a spectrum-sliced wavelength-division-multiplexed passive optical network with the channel spacing of 25 GHz, where even and odd channels are spectrum sliced separately using a pair of 50-GHz arrayed-waveguide gratings (AWGs). The 50-GHz AWGs have an offset of 25 GHz with respect to each other. Similarly, the demultiplexing is done using a pair of 50-GHz AWGs for even and odd channels separately. Our use of 50-GHz AWGs gives better bit-error rate performances than using 25-GHz AWGs in a conventional way. With 50-GHz AWGs, the channel bandwidth is increased about two times larger than using 25-GHz AWGs. Moreover, the increased spectral overlap between adjacent channels produces relatively small crosstalk since the channels are incoherent and their intensity noise is absorbed by reflective semiconductor amplifiers. The 25-GHz spaced spectrum-sliced WDM passive optical network can be realized more easily using 50-GHz AWGs since 50-GHz AWGs are more available in the market than 25-GHz AWGs.

Upstream WDM-PON transmission scheme based on PDM-OOK modulation and digital coherent detection with dual-modulus algorithm.

Wavelength-division-multiplexing passive optical network (WDM-PON) is a promising architecture for next-generation access networks because of its large bandwidth, protocol transparency and scalability. In this paper, we propose a cost-effective, high-speed upstream WDM-PON scheme adopting polarization division multiplexed (PDM) on-off keying (OOK) modulation at the optical network unit (ONU) and digital coherent/self-coherent detection with a novel blind dual-modulus equalization algorithm at the optical line terminal (OLT). As such, the upstream capacity can be directly enhanced at low ONU expenditure, and receiver sensitivity as well as power budget can be also improved. Enabled by the scheme, 40-Gb/s upstream transmission in 80-km WDM-PON is experimentally demonstrated.

Experimental demonstration of the real-time online fault monitoring technique for chaos-based passive optical networks

In this paper, a real-time online fault monitoring technique for chaos-based passive optical networks (PONs) is proposed and experimentally demonstrated. The fault monitoring is performed by the chaotic communication signal. The proof-of-concept experiments are demonstrated for two PON structures, i.e., wavelength-division-multiplexing (WDM) PON and Ethernet PON (EPON), respectively. For WDM PON, two monitoring approaches are investigated, one deploying a chaotic optical time domain reflectometry (OTDR) for each transmitter, and the other using only one tunable chaotic OTDR. The experimental results show that the faults at beyond 20km from the OLT can be detected and located. The spatial resolution of the tunable chaotic OTDR is an order of magnitude of centimeter. Meanwhile, the monitoring process can operate in parallel with the chaotic optical secure communications. The proposed technique has benefits of real-time, online, precise fault location, and simple realization, which will significantly reduce the cost of operation, administration and maintenance (OAM) of PON.

ZTE’s perspective on applying OFDM-PON in next converged optical and wireless networks

Driven by ZTE and other telecom vendors and operators in order to meet the ever increasing bandwidth demand from fixed optical network users and mobile backhaul/fronthaul services, the latest next generation passive optical network (NGPON2) is being standardized by Full Service Access Network (FSAN) and International Telecommunication Union (ITU-T) which consists of two separated sub-systems, hybrid time- and wavelength-division multiplexing PON (TWDM-PON) and point-to-point wavelength- division multiplex (PtP WDM). The TWDM-PON will be used for traditional residential, business and wireless backhaul services which are not sensitive to time delay and delay variation, whereas the PtP WDM is mainly used for emerging wireless fronthaul service which is very sensitive to the time delay and time delay variation. However, as a main international standards’ contributor, ZTE thinks for those operators who offer multiple-level of services to both residential, business and mobile backhaul/fronthaul users, this obviously raises significant economic and power concerns by demanding to deploy two separated systems. Therefore, in this paper, for the first time, ZTE proposes a new converged optical and wireless integrated network architecture and topology by applying orthogonal frequency division multiplexing (OFDM) PON technology, which is able to simultaneously support residential, business and mobile backhaul/fronthaul services in terms of meeting the requirements of both time delay sensitive and non-sensitive services, and also address the economic and power concerns compared with conventional technologies. This architecture is further investigated and analyzed in depth on functional block, Quality-of-service (QoS), synchronization and deployment considerations. Also ZTE reports in this paper the first 40Gbps OFDMPON prototype in which eight wavelengths each with 5Gbps Ethernet data via 10G-PON encapsulation method (X-GEM) and 10G-PON transmission convergence (X-GTC) framing are demonstrated.

TWC and AWG based optical switching structure for OVPN in WDM-PON

With the rapid development of optical elements with large capacity and high speed, the network architecture is of great importance in determing the performance of wavelength division multiplexing passive optical network (WDM-PON). This paper proposes a switching structure based on the tunable wavelength converter (TWC) and the arrayed-waveguide grating (AWG) for WDM-PON, in order to provide the function of opitcal virtual private network (OVPN). Using the tunable wavelength converter technology, this switch structure is designed and works between the optical line terminal (OLT) and optical network units (ONUs) in the WDM-PON system. Moreover, the wavelength assignment of upstream/downstream can be realized and direct communication between ONUs is also allowed by privite wavelength channel. Simulation results show that the proposed TWC and AWG based switching structure is able to achieve OVPN function and to gain better performances in terms of bite error rate (BER) and time delay.

Simultaneous generation of wavelength division multiplexing PON and RoF signals using a hybrid mode-locked laser

The use of millimeter-wave (mm-wave) frequencies has been proposed to overcome the imminent saturation of the ultra high frequency band, justifying research on radio over fiber (RoF) networks as an inexpensive and green solution to distribute multi-Gbps signals. Coincidently, telecommunication operators are investing a significant effort to deploy their passive optical network (PON) infrastructure closer to the users. In this work, we present a novel cost-efficient architecture based on a hybrid mode locked laser capable to simultaneously generate up-to 5 wavelength division multiplexing PON and RoF channels, being compatible with the 50-GHz ITU frequency grid. We analyze the limits of operation of our proposed architecture considering the high modal relative intensity noise induced by mode partition noise, as well as fiber impairments, such as chromatic dispersion and nonlinearities. The feasibility of generation and transmission of 5×10-Gbps PON and 5×5-Gbps RoF using orthogonal frequency division multiplexing up to 50km has been demonstrated through realistic numerical simulations.

Statistical UDWDM-PONs Operating With ONU Lasers Under Limited Tunability

We explore a new wavelength management for ultradense wavelength division multiplexing-passive optical network with randomly distributed optical network unit (ONU) wavelengths, controlled with limited thermal tunability. Static and dynamic wavelength assignment paradigms and heuristic assignment schemes for spectrum management are proposed, simulated, and compared. ONU acceptances in activation processes and ONU availability ratios up to 99.99% are obtained in standard environmental conditions.

A TWDM-PON with Advanced Modulation Techniques and a Multi-Pump Raman Amplifier for Cost-Effective Migration to Future UDWDM-PONs

Dense wavelength-division multiplexing passive optical networks and ultra-dense wavelength-division multiplexing passive optical networks are strong candidates to future next-generation passive optical network stage 3 access networks in order to satisfy increasing bandwidth demand, but their deployment is still a great challenge for telecommunication operators. Time and wavelength division multiplexed PON (TWDM-PON) has already been chosen by ITU-T as one of the best architectures in brownfield contexts to allow the reuse of the optical distribution network. Our proposal exploits the advantages of TWDM in order to reach a balance between coexistence with legacy systems and gradual and cost-effective migration towards pure wavelength division multiplexed PON (WDM-PON). In order to fulfill this aim, with reference to downstream traffic enhancement, two main novelties are presented: 1) the use of a multi-pump Raman amplifier (MRA) to satisfy the future necessity of large gain bandwidth; 2) the introduction of advanced modulation techniques to increase spectral efficiency and the future number of user channels (a less than 7 GHz-wide channel bandwidth providing 10 Gb/s bitrate has been demonstrated). A coherent system has been also proposed and its main impairments have been evaluated. The MRA has been accurately optimized to minimize power consumption without compromising performances. In the upstream direction, a semiconductor optical amplifier has been considered. The performances of the proposed TWDM-PON have been predicted through numerical simulations based on a system-level commercial CAD software.

Fifty-five km reach, bidirectional, 400 Gb/s (40 \times 10 Gb/s), channel-reuse DWDM–PON employing a self-wavelength managed tunable laser

We experimentally demonstrate a channel-reuse bidirectional 10 Gb/s/λ long-reach dense wavelength-division multiplexing passive optical network (DWDM-PON) and an optical beat-noise-based automatic wavelength control method for a tunable laser used in a colorless optical network unit (where λ=wavelength). A 55 km, bidirectional, 400 Gb/s (40×10 Gb/s) capacity channel-reuse transmission with 100 GHz channel spacing is achieved. The transmission performance is also measured with different optical signal to Rayleigh backscattering noise ratios and different central wavelength shifts between upstream and downstream in the channel-reuse system.

Performance Analysis of WDM-PON System Based on Optimized Remotely Pumped Erbium-Doped Fiber Amplifier (EDFA) Parameter

AbstractIn this paper, the performance of wavelength division multiplexing-passive optical network (WDM-PON) system using the erbium-doped fiber amplifier (EDFA) is optimized and evaluated. The optimization is analyzed by finding the EDFA length range at which the output power produced are the highest and the pump power range at which the gain flatness produced are within the effective range (0.3 dB). After the optimization process, the optimized EDFA system produces the gain of 26.6±0.292 dB, noise figure of 3.82 dB and output power of 7 dBm and the system is then implemented into WDM system. The performance of WDM system is compared against the system without EDFA in terms of bit error rate (BER). Results obtained prove that the proposed system with the EDFA consistently performs better than the conventional system.