Wavelength Reuse Research Articles

A routing and wavelength assignment scheme supporting multiple light-source nodes in multi-carrier-distributed optical mesh networks with wavelength reuse

This paper proposes a routing and wavelength assignment (RWA) scheme that supports multiple light-source nodes to minimize the number of required wavelengths for wavelength-reusable multi-carrier-distributed (WRMD) mesh networks. These networks use a light source, called the multi-carrier light source (MCLS), to ease the difficulty of controlling many light source devices. Moreover, they are able to reuse optical carriers for improving the effectiveness of wavelength usage. Since the WRMD network suffers constraints different from those of the conventional wavelength division multiplexing (WDM) network, an RWA scheme for the WRMD network with a single light source was recently developed. To use the resources of large-scale networks efficiently, there may be a need to have more than one MCLS node. In this paper, we first formulate the RWA problem as the integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths to satisfy the given lightpath setup requests. A heuristic RWA scheme is then introduced to solve the RWA problem in practical times. Simulation results show that the proposed heuristic RWA scheme for the WRMD network achieves a near-optimum number of wavelengths. In addition, optimizing MCLS node location is shown to reduce the number of required wavelengths for lightpath establishment.

Bidirectional multiband radio-over-fiber system based on polarization multiplexing and wavelength reuse.

A polarization multiplexing technique based on phase-shift-induced polarization modulation-to-intensity modulation (PloM-to-IM) convertor and a Mach-Zehnder modulator (MZM) is proposed to generate multi-band signals. Successful transmission of the traditional radio frequency, microwave (MW) and millimeter wave (MMW) signals is simultaneously achieved. Meanwhile, the intensity-constant optical carrier (OC) is reused for upstream 25-km transmission.

Fiber link tests of wavelength reuse after amplitude erasure in semiconductor optical amplifier

ABSTRACTPropagation in a 25‐km fiber link with wavelength reuse based on amplitude modulation erasure by deep saturated ultralong semiconductor optical amplifier is demonstrated up to 12.5 Gb/s. Downstream signals with modulation extinction ratio (ER) up to 10 dB were tested in links with standard and dispersion compensated fibers. The impact of bit rate and input ER over the wavelength reuse performance is investigated, including tests at diverse wavelengths to induce residual dispersion impairments. Despite the inherent spectral broadening occurring in the erasure process the upstream signals have good quality even after dispersive fiber links, as evidenced by BER characterization. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:132–137, 2015

Broadcast and Weight: An Integrated Network For Scalable Photonic Spike Processing

We propose an on-chip optical architecture to support massive parallel communication among high-performance spiking laser neurons. Designs for a network protocol, computational element, and waveguide medium are described, and novel methods are considered in relation to prior research in optical on-chip networking, neural networking, and computing. Broadcast-and-weight is a new approach for combining neuromorphic processing and optoelectronic physics, a pairing that is found to yield a variety of advantageous features. We discuss properties and design considerations for architectures for scalable wavelength reuse and biologically relevant organizational capabilities, in addition to aspects of practical feasibility. Given recent developments commercial photonic systems integration and neuromorphic computing, we suggest that a novel approach to photonic spike processing represents a promising opportunity in unconventional computing.

A routing and wavelength assignment scheme in multi-carrier-distributed optical mesh networks with wavelength reuse

This paper proposes a routing and wavelength assignment (RWA) scheme that minimizes the number of required wavelengths for wavelength-reusable multi-carrier-distributed (WRMD) mesh networks. These networks have two unique features. First, only one light source, called the multi-carrier light source (MCLS), is required, which eases the difficulty of controlling many light source devices. Second, optical carriers are reused to improve the efficiency of wavelength usage. Since there are differences between the WRMD network and the conventional network, an efficient RWA scheme for the WRMD network is needed for wavelength-resource-efficient lightpath establishment. To realize efficient wavelength usage, we first formulate the RWA problem as an integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths to satisfy the given requests. For large-scale networks, the ILP approach is not practical solution times. A heuristic RWA scheme is introduced in this paper to solve the RWA problem. Simulation results show that the proposed heuristic scheme with two carrier regenerations for the WRMD network approaches the near-optimum number of wavelengths. In addition, the optimum placement of the MCLS node is shown to reduce the number of required wavelengths for lightpath establishment, and achieve the optimum number of wavelengths.

Full-duplex radio over fiber system with optimum optical carrier to sideband ratio and wavelength reuse

A full-duplex radio over fiber system with optimum optical carrier to sideband ratio (OCSR) of 0 dB and wavelength reuse for uplink are proposed. At the central office, single-sideband modulation with OCSR larger than 0 dB is realized based on optical injection. At the base station, a notch filter with the notch depth corresponding to the OCSR of the transmitted signal is used to achieve the optimum OCSR of 0 dB. The reflected weakly modulated carrier is reused as the carrier for upload signals. A simulation is carried out to verify the proposed system. Results show that the download 60-GHz-RF signal is almost not affected by the fiber chromatic dispersion, and the power penalty after transmission over a 50-km single-mode fiber is negligible in uplink and is only 1.27 dB in downlink.

Wavelength assignment for all-to-all broadcast in WRMD WDM linear array and ring

This paper proposes a wavelength assignment method for all-to-all broadcast in wavelength reusable multi-carrier distributed (WRMD) wavelength division multiplexing (WDM) linear array and ring networks with wavelength reuse. An expression on the minimum number of wavelengths required to establish all-to-all broadcast is also derived for the networks. It is observed that one carrier regeneration per wavelength significantly reduces the number of wavelengths compared to that without carrier regeneration. The results also show that regenerating carriers more than once has little effect on the required number of wavelengths.

A novel optical millimeter-wave signal generation approach to overcome chromatic dispersion

In this paper, a novel frequency octupling approach for optical millimeter-wave signal generation to overcome chromatic dispersion is proposed and demonstrated. The frequency octupling mm-wave with the baseband signal carried only by −4th order sideband is generated by properly adjusting a series of parameters, which are the modulation constant, the gain of baseband signal, the direct current bias and the different phase of the modulation arms. As the optical millimeter-wave signal is transmitted along the fiber, there is no time shift caused by chromatic dispersion. Theoretical analyses and simulated results show that when the optical mm-wave carrying 2.5Gbps baseband signal transmits a distance of over 110km, the eye diagram still keeps open and clear. The power penalty is about 0.4dB after the optical signal transmits over 40km. In additions, given the +4th order sideband carries no data, a full-duplex RoF link based on wavelength reuse is built for the uplink. The bidirectional 2.5Gbps baseband signal could successfully transmit over 40km with about 0.8dB power penalty in the simulation. Both theoretical analyses and simulation results show that the full-duplex RoF link has good performance.

Wavelength Reuse in a UWB Over WDM-PON Based on Injection Locking of a Fabry–Pérot Laser Diode and Polarization Multiplexing

Wavelength reuse in a symmetric ultra-wideband (UWB) over wavelength-division-multiplexing passive optical network based on injection locking of a Fabry-Pérot laser diode (FP-LD) and polarization multiplexing is proposed and experimentally demonstrated. In the proposed scheme, the downstream UWB signal and baseband signal are generated and polarization multiplexed in the central station and sent to a base station (BS) over an optical fiber. At the BS, one of the downstream signals is selected to injection lock the FP-LD. It is demonstrated theoretically and experimentally that the upstream service performance is less sensitive to the modulation depth of the downstream UWB signal than the baseband signal, and the use of the downstream UWB signal as the injection signal would contribute to a better transmission performance for both the downstream and upstream services. Thus, the downstream UWB signal is selected as the injection signal. An experiment is performed. When the FP-LD is injection locked by a downstream UWB signal, a clear optical carrier is generated which is reused for upstream UWB and baseband transmission. A bidirectional point-to-point transmission of 1.25 Gb/s UWB signal and 10 Gb/s baseband signal over 25-km single-mode fiber using a single wavelength is demonstrated. The bit error rate performances and the eye diagrams for both downstream and upstream transmissions are measured.

Limits on High Bit Rate Wavelength Reuse Using Ultralong Semiconductor Optical Amplifier

Amplitude data erasure for wavelength reuse using an ultralong semiconductor optical amplifier (UL-SOA) in saturation is demonstrated for optical carriers modulated up to 56 Gb/s (NRZ). The erasing performance efficiencies with different input bit rates are presented, as well as the influences of parameters such as input (amplitude) extinction ratio, optical power, wavelength, and UL-SOA bias current. Bit error rate (BER) curves show that the remodulated (upstream) signal has enough quality to be applied in wavelength division multiplexing-passive optical networks (WDM-PON) systems, when very high bit rates or high input extinction ratio are needed and spectral broadening in the erased carrier could be accepted.

Wavelength reuse in a bidirectional radio-over-fiber link based on cross-gain and cross-polarization modulation in a semiconductor optical amplifier

Wavelength reuse in a bidirectional radio-over-fiber link is proposed and demonstrated based on the cross-gain modulation (XGM) and the cross-polarization modulation in a semiconductor optical amplifier (SOA). With a polarization beam splitter placed at the remote antenna unit, the polarization-modulated signal generated at the SOA is converted into noninverted and inverted intensity-modulated signals. The noninverted signal is used to cancel the inverted XGM-induced intensity-modulated signal to form a clean optical carrier for wavelength reuse in upstream signal transmission, while the inverted intensity-modulated signal is combined constructively to enhance the XGM-induced signal, providing robust downlink service. A bidirectional transmission of 5GHz RF signal carrying a 50MBaud 16 quadrature amplitude modulation baseband signal is experimentally implemented. The error vector magnitude degradation due to the fiber transmission for both the downlink and uplink signal is about 0.2%.

Wavelength Reuse in a UWB Over Fiber System Based on Phase-Modulation to Intensity-Modulation Conversion and Destructive Interferencing

A novel wavelength reuse scheme based on phase-modulation to intensity-modulation (PM-IM) conversion and destructive interferencing using a polarization modulator (PolM) and a fiber Bragg grating (FBG) in an ultra-wideband (UWB) over fiber (UWBoF) system is proposed and experimentally demonstrated. In the proposed scheme, a PolM and an FBG in the central station (CS) are used to generate intensity-modulated impulse UWB signal based on PM-IM conversion. The downstream UWB signal is sent to a base station (BS) over an optical fiber. At the BS, when the principle axis of the polarizer is aligned with one of the two orthogonal states of polarization (SOPs), the downstream UWB signal is received and detected. When the principle axis of the polarizer is oriented at a special angle to one of the two orthogonal SOPs, a clear optical carrier without intensity modulation is generated, which is then reused for upstream UWB data transmission. A theoretical analysis is performed which is verified by an experiment. A bidirectional point-to-point transmission of 1.25 Gb/s UWB signal over 25-km single-mode fiber (SMF) using a single light source from the CS is demonstrated. The receiver sensitivity and the BER performance for both downstream and upstream transmissions are measured.

Efficient Dynamic Modeling of the Reflective Semiconductor Optical Amplifier

Reflective semiconductor optical amplifier (RSOA) is considered a strong candidate to play an important role in realizing the next generation wavelength division multiplexing passive optical network, based on the wavelength reuse concept. Therefore, an accurate and efficient modeling of RSOA is of significant importance. We present a time-domain wideband model for simulation of spatial and temporal distribution of photons and carriers in a bulk RSOA. We provide a novel approach for efficient amplified spontaneous emission modeling, considering a tradeoff between the accuracy and the computational efficiency. The multiobjective genetic algorithm is utilized for parameter extraction. Experimental validation has been performed for continuous wave input, nonreturn to zero (NRZ) on-off keying, and quadrature phase-shift keying (QPSK) signaling pulses up to 40 Gb/s of bit rate, in both amplification and remodulation regimes. We further present systematic performance evaluation under remodulation scenario. Saturation, noise, chirp, and signal broadening are successfully predicted, while reducing the computational time compared to other wideband models.

FSK signal generation with wavelength reuse capability in 8 Gbit/s radio over fiber systems

In this paper, a technique was numerically implemented to generate a frequency shift keying (FSK) radio-over-fiber (RoF) signal in optical domain. Due to the oscillator free generation of FSK signal, this scheme is highly stable with reduced complexity and extremely cost effective. The remote heterodyne detection method was used to detect the signal, where beating occurs to detect the FSK signal. With this scheme, it is able to efficiently generate FSK signal in the range of 60 and 75 GHz at 8 Gbit/s and effectively transmit it over 80 km link without degrading the signal shape and quality. The nonlinear threshold (NLT) point of the system has also been numerically analyzed to estimate the nonlinear tolerance of the system. Besides, the impact of transmission distance and polarization mode dispersion (PMD) was evaluated. Furthermore, the wavelength reuse for the uplink was implemented in the scheme by reusing the same wavelength for uplink that was used for signal generation at downlink. The whole process was performed in optical domain. Thus this scheme is very cost effective as the overall architecture of RoF system is simplified.

Full-Duplex 4-PAM Transmission for Capacity Upgrade in Loop-Back PONs

We report for the first time on the feasibility of quaternary (4-ary) pulse amplitude modulation (4-PAM) for both downstream (DS) and upstream (US) directions in a full-duplex passive optical network (PON) with wavelength reuse. The scheme is validated with a simple, low-cost, and colorless optical network unit (ONU) exploiting the all-optical carrier recovery scheme. The ONU employs a high-finesse optical filter with periodic frequency response for carrier extraction and data erasure of the DS signal. A cascade of two semiconductor optical amplifiers (SOAs) amplifies and modulates the recovered carrier with the 4-PAM US data-stream. The proposed scheme constitutes a migration scenario towards low-cost TDM/WDM PONs with currently deployed hardware equipment, ensuring full-duplex transmission up to 26 km, with higher spectral efficiencies and auspicious wavelength allocation.

Wavelength reuse in a bidirectional UWB over fiber system

Wavelength reuse in a bidirectional UWB over fiber system using a polarization modulator (PolM) and an electro-absorption modulator (EAM) is proposed and experimentally demonstrated. Since the PolM functions as a special phase modulator that supports phase modulation along the two principal axes with opposite modulation indices and the EAM is a polarization-independent component, the signals due to the phase-modulation to intensity-modulation (PM-IM) conversion along the two orthogonal directions in the upstream link will be complementary and cancelled out, thus the impact of the downstream signal to the upstream transmission due to the PM-IM conversion is fully eliminated. Error-free bidirectional transmission of a 1.25-Gbps UWB signal over 17 km single-mode fiber (SMF) is demonstrated. A power penalty due to the wavelength reuse for upstream transmission is measured to be as low as 0.2 dB.

A full duplex radio-over-fiber transmission of OFDM signals at 60 GHz employing frequency quintupling optical up-conversion

This work proposes a full-duplex 60-GHz Radio-over-Fiber Orthogonal-Frequency-Division-Multiplexing (ROF-OFDM) system employing a frequency quintupling optical up-conversion scheme. To avoid the subcarrier signal beat interference (SSBI) due to dispersion-induced fading, a modified single sideband modulation scheme is proposed for the 10-Gbps QPSK-OFDM down-link signal. The power penalty of less than 2-dB was observed after a 50-km single mode fiber (SMF) and 4m wireless transmission. Wavelength reuse with a 1.25-Gbps OOK for up-link transmission is also demonstrated with a receiver penalty of less than 0.5-dB following 50-km SMF transmission.

Review and Performance Analysis on Routing and Wavelength Assignment Approaches for Optical Networks

For the past several years, traffic especially, Internet traffic has been increased tremendously and this growth demands for a high-speed communication network such as optical network. Routing and Wavelength Assignment (RWA) is one of the key tasks for the optical network, due to its information transparency and wavelength reuse characteristics. In this paper, we discuss different conventional RWA approaches in the wavelength-routed optical networks and compare them with our proposed Priority-based RWA (PRWA) scheme under wavelength continuity constraint. The performance analysis of different conventional RWA approaches including our PRWA scheme is conducted in terms of blocking probability. Finally, we address a number of research issues that appear to us to be both important and challenging.

Direct DPSK modulation of chirp-managed laser as cost-effective downstream transmitter for symmetrical 10-Gbit/s WDM PONs

This paper proposes the use of chirp-managed lasers (CML) as cost-effective downstream (DS) transmitters for next generation access networks. As the laser bandwidth is as high as 10 GHz, the CML could be directly modulated at 10 Gbit/s for downstream transmission in future wavelength division multiplexing passive optical networks (WDM PON). The laser adiabatic chirp, which is the main drawback limiting the transmission performance of directly modulated lasers, is now utilized to generate phase-shift keying (PSK) modulation format by direct modulation. At the user premise, the wavelength reuse technique based on reflective colorless upstream transmitter is applied. The optical network unit (ONU) reflects and orthogonally remodulates the received light with upstream data. A full-duplex transmission with symmetrical 10-Gbit/s bandwidth is demonstrated. Bit-error-rate measurement showed that optical power budgets of 29 dB at BER of 10(-9) or of 36 dB at BER of 10(-3) could be obtained with direct phase-shift-keying modulation of CML which proves that the proposed solution is a viable candidate for future WDM-PONs.

Transmission of 100 GHz w‐band frequency MIMO‐OFDM signals with 90 Gbps downstream and 30 Gbps upstream using radio over fiber system

AbstractIn this article, we propose and demonstrate an orthogonal frequency division multiplexing‐radio over fiber (OFDM‐ROF) system based on three channels sextupling‐frequency scheme using an external modulation of a distributed feedback laser diode (DFB‐LD) and dual drive Mach–Zehnder modulator (DD‐MZM) for carrying 100 GHz W‐band frequency multiple‐input multiple‐output (MIMO)‐OFDM signals with 90 Gbps downstream. MIMO‐OFDM algorithms effectively compensate for impairments in the wireless link. Without using costly W‐band components, a transmission system with 50 km single mode fiber (SMF) and 4 m wireless transmission operation at 100 GHz is experimentally validated. The power penalties for MIMO‐OFDM signals of base stations are less than 3 dBm. For the upstream transmission, wavelength reuse with 30 Gbps 4QAM upstream signals is experimentally demonstrated. The minimum optical spectral gap between residue downstream OFDM band and upstream OFDM band that guarantees a tolerable amount of optical interference has been determined through experiment. The frequency of local oscillator is reduced due to frequency sextupling scheme. The cost of the proposed system is largely reduced. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:93–99, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27251