Bidirectional radio-over-fiber systems with SSB modulation and wavelength reuse based on injection-locked semiconductor lasers

A 60-GHz bidirectional radio-over-fiber （RoF） system using two-carrier-injected distributed feedback （DFB） laser is proposed and demonstrated to realize optical single sideband （SSB） modulation for downlink.An injection-locked Fabry-P＇erot laser is also carried out to realize wavelength reuse in uplink.Transmission of 2.5 Gb/s on a 60-GHz carrier for downlink and 622-Mb/s baseband signal for uplink are both successfully demonstrated over 50-km single mode fiber without chromatic dispersion compensation.     

Design of millimeter-wave fiber-wireless downlink with remote local-oscillator delivery by using dual-electrode Mach-Zehnder modulators configured for optical single-sideband modulations

An optical fiber-wireless system operating in millimeter-wave (MMW) bands may include numerous optical remote access points (RAPs) of which the cost is critical to implement such systems in real market. In this paper, we design an optical fiber communication system for MMW optical fiber downlink transmission with remote MMW local-oscillator (LO) delivery for intermediate frequency (IF) fiber uplink transmission. The new design is based on two dual-electrode Mach-Zehnder modulators in parallel both configured for optical single-sideband modulations. By using the proposed design, a conventional RAP can be simplified in structure to reduce the cost. Our numerical results show that, with the proposed design, 1-Gbit/s binary-phase-shift-keying (BPSK) data at a 42-GHz sub-carrier frequency can be transmitted over a 20-km standard single-mode optical fiber followed by a wireless transmission of several kilometers. Moreover, a MMW LO at 37-GHz frequency can be remotely delivered over tens of kilometers of a standard single-mode fiber with acceptable deterioration in the LO phase noise for IF uplink fiber transmission.     

Generation of optical carrier suppression millimeter-wave signal using one dual-parallel MZM to overcome chromatic dispersion

In this paper, we have proposed a novel approach to generate optical carrier suppression (OCS) mm-wave with signal only carried by one first-order sideband using a dual-parallel MZM in radio-over-fiber (RoF) system, and the transmission performance was also investigated. As the optical mm-wave signal is transmitted along the fiber, there is no time shift of the data symbols resulting from the group velocity dispersion in the fiber because the signal is only modulated on one sideband. The simulation results showed that the eye diagram keeps open and clear even when the optical mm-wave signals are transmitted over 96-km and the power penalty is about 1-dB after fiber transmission distance of 60-km, which is quite consistent with our theoretical analysis. Furthermore, the proposed OCS optical mm-wave generation approach is also used in a full-duplex RoF link based on wavelength reuse at the base station for the uplink due to another pure sideband without carrying data. The bidirectional 2.5-Gbit/s data is successfully transmitted over 40-km standard single mode fiber with less than 0.5-dB power penalty in the simulation. Both the unidirectional RoF downlink and the full-duplex RoF system have good performance.     

Linearization and dispersion tolerable technique for remote access unit in uplink RoF system based on gain-saturated RSOA cascaded EAM

A novel scheme of a remote access unit which is based on an electroabsorption modulator cascaded by a gain-saturated reflective semiconductor optical amplifier is proposed to improve a transmission performance of uplink signal. The cascaded gain-saturated reflective semiconductor optical amplifier plays a role in enhancing linearity of the electroabsorption modulator as well as suppressing dispersion-induced carrier suppression in the uplink transmission using its nonlinear gain property. In the proposed scheme, carrier-to-interference ratio of transmitted 10-GHz band uplink signal was improved by 10.7 dB and the dispersion-induced carrier suppression of 5.65-GHz RF carrier was greatly mitigated by 33.4 dB through the 75.6-km optical link.     

基于综合光学调制技术的光纤无线双向通信系统设计

提出并研究了一种使用单光源的光纤无线双向传输系统.该系统只需在中心站配置一个可调谐激光器,以产生频率恒定的激光光源,通过综合光学调制（频率调制、强度调制）技术将基带信号调制到光载波上,最终形成60 GHz毫米波下行信号|同时,相同的光载波在基站被重用,作为上行链路传输光源.系统结合光载波重用技术和综合调制技术特点,合理利用资源,基站结构更为简化.仿真结果表明,该系统可以将速率达2.5 Gbit/s的数据在单模光纤中双向传输20 km,功率代价小于0.5 dB,相对已有的技术方案,该传输系统在传输功率、传输距离、传输性能方面具有明显优势.     

Alternative Wired and 60-GHz Wireless Full Duplex Access Based on a Polarization Orthogonal Dual-Tone Optical Millimeter-Wave Signal

Abstract

A novel full duplex fiber wireless link providing alternative wired and 60-GHz wireless access is proposed based on a polarization orthogonal dual-tone optical millimeter-wave signal. In a hybrid optical network unit, the downlink optical signal can be decomposed as a single-sideband optical millimeter-wave signal (baseband optical signal) for wireless (wired) access by a polarization controller and polarization beam splitter. The uplink optical carrier abstracted from the downlink optical signal makes the hybrid optical network unit free from the optical source. The simulation results show that both downlinks and uplinks for either wired or wireless access can maintain quite good performance over 60 km of fiber.     

10 Gb/s WDM-PON based on FP-LDs injection locked by downlink optical carrier

We propose and demonstrate a 10 Gb/s wavelength division multiplexed passive optical network (WDM-PON) where subcarriers are employed to transmit the downstream data and optical carriers of the downlink subcarrier modulated (SCM) lights are reused to injection lock Fabry-Perot laser diodes (FP-LDs) for uplink transmission. Experiment results show that a very good BER performance can be achieved for both uplink and downlink at 10 Gb/s. The impact of optical carrier to subcarrier ratio and wavelength mismatching is also investigated.     

Colorless gigabit WDM-PON link using injection locking and electro-absorption transceiver

In this paper, a novel colorless wavelength division multiplexing-passive optical network (WDM-PON) system using injection locking and electro-absorption transceiver (EAT) is proposed and demonstrated experimentally. This system has advantages, high data transmission, small downlink signal effect to uplink signal and less polarization sensitivity, compared to the system using reflective semiconductor optical amplifier (RSOA). Downlink signal modulates the right side carrier of the double side band signal by using injection locking. EAT functions as both photo detector in downlink signal and modulator for uplink signal, simultaneously. A possible cross absorption modulation effect from the EAT is analyzed experimentally. Bidirectional transmission of 1.25 Gbps and 622 Mbps for downlink and uplink, respectively, were verified through 23 km standard single mode fiber (SSMF).     

Novel 60 GHz RoF system with optical single sideband mm-wave signal generation and wavelength reuse for uplink connection

In order to improve RF frequency to achieve higher bandwidth and larger capacity, we propose a novel scheme to generate optical single sideband (SSB) millimeter-wave, in which frequency doubling of local radio frequency (RF) is obtained by using one integrated Mach–Zehnder modulator (MZM), and we theoretically investigate the generating principle of SSB. The optical SSB modulation scheme is employed to generate 60 GHz optical mm-wave and the 2.5 Gb/s baseband signal is simultaneously up-converted at the central station (CS) for downlink transmission, and the optical carrier is reused for uplink connection at the base station (BS). The full-duplex 2.5 Gb/s data are successfully transmitted over 40 km standard single-mode fiber (SMF-28) for both uplink connection and downlink connection with less than 2-dB power penalty. Results show the novel 60 GHz RoF system with optical SSB mm-wave signal generation using optical frequency doubling is feasible and we can obtain simple cost-efficient configuration and good performance over long-distance transmission.     

Investigation on wavelength re-modulated bi-directional passive optical network for different modulation formats

In this paper, the cost effective bi-directional passive optical network architecture with wavelength remodulated scheme is investigated. To realize the cost-effective PON, remodulation scheme is used, in which the downstream optical signal is reused as a carrier for the upstream transmission as it eliminates the need for an extra laser source at optical network units. The performance of proposed passive optical network is analyzed and compared for various modulation formats such as Non Return to Zero (NRZ), Return to Zero (RZ) and On–Off Keying (OOK) with 64 optical networks units (ONUs) at different traffic speed for downlink and uplink, respectively. It has been observed that the most suitable data format for proposed PON network is NRZ. Further the proposed system performance is compared with the current state-of-the-art PON architectures.     

10 Gb/s symmetric WDM-PON using stable multi-longitudinal mode Brillouin/SOA fiber laser as upstream colorless source

We propose a stable multi-longitudinal Brillouin/semiconductor fiber laser(BSFL) as the upstream source in a bidirectional single-fiber wavelength-division multiplexing-passive optical network(WDM-PON).The downstream wavelength serves as the pump of the BSFL.Brillouin-frequency-shifted(～10.8 GHz) upstream carrier is generated to suppress the Rayleigh backscattering and back reflection-induced crosstalk.The stable multi-longitudinal operation of the BSFL,attributed to the four-wave mixing(FWM) effect in the semiconductor optical amplifier(SOA) reduces the difficulty of generating a stable single-longitudinal fiber laser-based upstream carrier.Bidirectional symmetric transmission at 10 Gb/s over a 12.5-km single mode fiber with less than 2-dB power penalty is demonstrated.     

Investigation of broadcasting signal overlay using high-frequency filtering characteristics of RSOA in ASE seeded WDM access network

The simultaneous baseband and broadcasting signal transmission based on wavelength division multiplexing-passive optical network access network are proposed and their experimental verifications are shown. Amplified spontaneous emitting source modulated by broadcasting signal in radio frequency band at reflective semiconductor optical amplifier is provided as seed source for wired signal modulation. The filtered amplified spontaneous emitting source is aligned to each channel and modulated by the downlink baseband signal at RSOA. Simultaneous downstream transmission of baseband and broadcasting signals over 23-km SMF is experimentally verified. Mutual interference between broadcasting and baseband signals, nonlinearity by two tone analysis, and performance variation on temperature are investigated.     

160 km all-optical OFDM transmission system with inline chromatic dispersion compensation

An experimental demonstration of an all-optical sampling orthogonal frequency division multiplexing (AOS-OFDM) transmission system with inline chromatic dispersion (CD) compensation is carried out to test the nonlinear influence. With five subcarriers non-return-to-zero (NRZ) modulated, the total bit rate is 50 Gb/s without polarization multiplexing. The receiver end is highly simplified with direct detection using optical Fourier transform filter. After transmission in 160-km standard single-mode fiber (SSMF) link with 130-ps/nm residual CD, an optimum input optical power for the system performance is achieved.     

Gigabit-converged wired and wireless networks for simultaneous multi-services transmission

A novel architecture of converged radio-over-fiber(RoF) and wavelength division multiplexed passive optical network(WDM-PON) system,namely RoF-WDM-PON,is demonstrated.20-GHz 1-Gb/s radio frequency(RF) signals and 1-Gb/s baseband(BB) signals are simultaneously generated and transmitted using optical carrier suppression(OCS) modulation techniques.The proposed scheme is compatible with the conventional RoF and PON system.25-km single-mode fiber(SMF) transmission is successfully achieved.     

Optical power equalization for upstream traffic with injection-locked Fabry-Perot lasers in TDM-PON

An optical power equalization of upstream traffic in time-division-multiplexed passive optical network (TDM-PON) based on injection-locked Fabry-Perot lasers has been experimentally investigated. The upstream transmitters with stable spectrum are achieved by using an external injection light source in the optical line terminal (OLT). The different upstream powers can be equalized by injection locking a Fabry-Perot laser diode (FP-LD) biased below threshold current in OLT. The dynamic upstream power range from − 8.5 to − 19.5 db m is reduced to a 1.6 dB maximal power variation, when the uplink signal is directly modulated at 1.25 Gb/s.     

A full-duplex radio-over-fiber system using direct modulation laser to generate optical millimeter-wave and wavelength reuse for uplink connection

In this paper, we present a full-duplex radio-over-fiber system incorporating both optical millimeter-wave (mm-wave) generation and wavelength reuse for uplink connection. The optical double sidebands (DSB) signal is generated by using only one inexpensive broadband direct modulation laser (DML), to which a mixing RF signal is applied. An optical interleaver is then used to separate the first-order optical sidebands from the optical carrier of optical DSB signal. The separated first-order optical sidebands are beat to generate mm-wave signal that has double the frequency of the RF drive signal, while the separated optical carrier is reused as light source to remodulate uplink signal. Both detailed theoretical analysis and experiments to demonstrate the feasibility of the proposed system are presented. Experiment result shows that the bidirectional 2.5 Gb/s data can be successfully transmitted over 40 km standard single-mode fiber (SSMF) with less than 2 dB power penalty.     

40 Gbit/s Transparent Network Based on Wavelength-Selective Optical Cross Connect

This paper discusses a 40-Gbit/s transparent optical network focusing on the optical transport performance. We show 1200-km transmission with two WSOXC’s spaced by 400 km. In addition, network control issues are briefly addressed.     

Full-Duplex Link Providing Alternative Wired and Wireless Broadband Access for the Wavelength-Division Multiplexing Passive Optical Network with a Uniform Converged Signal Format

Abstract

A full-duplex link implementing alternative wired and wireless access for wavelength-division multiplexing passive optical network is proposed with the uniformed three-tone converged optical signal, which provides a wired or wireless downlink access signal alternatively and an uplink optical carrier. The uplink optical carrier reversed by the converged optical signal makes the hybrid optical node unit free from the optical source. The simulation results show that the full-duplex link with a 10-Gb/s 16-quadrature amplitude modulation (16-QAM) downstream and 5 Gb/s binary upstream can provide both wired access with a bit-error rate below 10^?9 and radio-over-fiber-based wireless access with a bit-error rate below 10^?7 over 40 km of fiber without an optical source and optical amplifier in the hybrid optical node unit.     

Experiment on 60-GHz MMW transmission performance in an optical fiber and wireless system

We experimentally investigate the transmission performance of 60-GHz signals over standard single-mode fiber (SSMF) and wireless links at different bit rates. Experimental results show that in a transmission of over 10-km SSMF and 1.3-m wireless link, bit rate reaches up to 5 Gb/s and bit error rate (BER) is less than 10 4 . The main limiting factor in such radio-over-fiber (ROF) systems is intersymbol interferences caused by the so-called walk-off effect when BER is below 10 8 . In addition, a transmission of over 20-km SSMF without chromatic dispersion compensation is briefly investigated. For a BER of 10 8 , the optical penalty is 2 dB.     

Bidirectional Wavelength Reconfigurable Module Based on Tunable Fiber Bragg Grating and Remote Pump Amplifier

Abstract

This article presents a novel bidirectional wavelength reconfigurable optical network utilizing a remotely pumped erbium-doped fiber amplifier and tunable fiber Bragg gratings. The system is experimentally demonstrated at a 10-Gb/s per channel over 20-km fiber span that verifies the metro-network range system performance. The achieved power penalty is less than 1 dB when compared to the back-to-back transmission link. An example of practical application where the proposed module is used as an add/drop multiplexer and a remote node in the bidirectional wavelength division multiplexing passive optical network system is described.