Wavelength Division Multiplexing Radio-over-fiber Research Articles

Performance Analysis of 8 * 112 Gbps (0.896 Tbps) WDM ROF Link Using 32 QAM - OFDM Modulation Scheme for Achieving Extended Range

We propose an advanced optical transport system utilizing higher order modulation formats and coherent detection. Our innovation introduces an 8 x 112 Gbps WDM ROF link using a 32 QAM-OFDM modulation scheme, capable for extending its reach. Our proposed research stands out from existing studies due to its distinctive use of the 32-QAM format and a 112Gbps data rate per channel, especially when considering a channel span of 3000 kilometers Our analysis covers Wavelength Division Multiplexing - Radio over Fiber (WDM-ROF) link systems, including a pre-optical amplifier within the link, one optical amplifier outside the channel loop span, and one within the loop span, representing distinct scenarios. We operated optical amplifiers in the gain-controlled mode. Remarkably, exclusive of employing precise dispersion or non-linearity improvement techniques, carried out simulations reveal optimal transmission distance for our anticipated system having considered specification parameters is 3000 Km. We conducted extensive simulations to assess the system performance in terms of Q-factor, ESE, and EVM over link spans ranging since 1000 to 15000 Kilometers.

Multiband RoF System with Good Transmission Performance Based on Additional SCS

A wavelength division multiplexing radio-over-fiber (WDM-RoF) system that can support multiband radio signals based on an additional subcentral station (SCS) is proposed and demonstrated in this paper. The dispersion characteristics of the multiband radio signals over fiber transmission are explored, and we exploit an improved transmission structure consisting of the central station (CS), the SCS, and base stations (BSs) to optimize the antidispersion performance of the proposed RoF system. At the SCS, a dual-drive Mach-Zehnder modulator (MZM) is employed to realize a cost-effective multiband radio signal generation of WDM signals with great spectral flatness, and an optical cross-connect unit is utilized to achieve a flexible distribution of different band radio signals for remote BSs. Based on the additional SCS, we establish a verification WDM-RoF system, which can support reliable transmission of multiband radio signals including 13 GHz, 26 GHz, 39 GHz, and 52 GHz. The WDM signals with each data rate at 2.5 Gbps are successfully transmitted over a 40 km standard single-mode fiber.

Study on increasing the capacity of RoF systems for long distance optical communication using solitons

In order to enable long distance communication, the light signal in Radio-over-fiber (RoF) technique is modulated by a radio signal. WDM (wavelength division multiplexing) technology is an effective way which can be used in the optical fiber feeder network to increase the capacity of RoF systems. In spite of the advantages RoF has nonlinear effects such as dispersion which can be mitigated by selecting appropriate dispersion management techniques. One of the challenges of WDM is the proper wavelength spacing. It must be properly designed so that signal interference does not occur. In this paper we try to review which dispersion management technique provides greater efficiency for long haul optical networks. The performance efficiency of different modulation techniques and different orders of modulation is also reviewed. So, by this work we try to propose a model which will provide better output power and low dispersion level which is the primary concern of any optical transmission system. The proposed model incorporates a WDM RoF system with soliton dispersion management system and the modulation technique employed is 64 QAM/DPSK and the results are analyzed in terms of Q-factor and Bit Error Rate (BER).

Monolithically integrated multi-section semiconductor lasers: Towards the future of integrated microwave photonics

Recent advances in monolithically integrated multi-section semiconductor lasers (MI-MSSLs) have propelled microwave photonic (MWP) technologies to new potentials with a compact, reliable, and green implementation. Much research has examined that MI-MSSLs can realize the same or even better MWP functions compared to discrete lasers by taking advantages of enhanced light–matter interactions. Here, we review these recent advances in this emerging field and discuss the corresponding photonic microwave applications. Three main kinds of MI-MSSL structures are demonstrated in general including passive feedback laser, active/amplified feedback laser, as well as monolithically integrated mutually injected semiconductor laser. The focus of this paper is on the MWP techniques based on the nonlinear dynamics of MI-MSSLs. The primary MWP applications considered in this paper cover from electro-optic conversion characteristics enhancement, photonic microwave generation, microwave photonic filter, to multi-wavelength laser array for wavelength division multiplexing radio-over-fiber (WDM-RoF) networks. Especially, the four special dynamic states of free-running oscillation, mode-beating self-pulsations (MB-SPs), period-one (P1) oscillation, and sideband injection locking are considered and demonstrated in detail for photonic microwave generation. We also take a look at the future prospects of the research directions and challenges in this area.

Full-duplex WDM-RoF system based on OFC with dual frequency microwave signal generation and wavelength reuse

Abstract A novel full-duplex wavelength division multiplexing radio-over-fiber (WDM-RoF) system based on optical frequency comb (OFC), which can generate dual frequency microwave signal simultaneously and realize wavelength reuse for uplink transmission, is proposed. In this proposal, OFC, which serves as the optical carriers of the WDM-RoF network, is performed by cascading two electro-absorption modulators (EAMs) and a frequency modulator (FM). The optical carriers are modulated by the radio frequency (RF) signal in LiNbO3 Mach-Zehnder modulator (LN-MZM) to produce multiple optical single sidebands (OSSB). The multiple OSSB signals are divided into multiple individual channels by AWG, and each channel contains two optical carriers and two corresponding +1 order sidebands. The first optical carrier of each channel is reflected by fiber bragg grating (FBG) and reused to provide the optical source for the uplink transmission in the base station (BS), which simplify the configuration of base station. Dual-frequency microwave signals are generated in the downlink by beating the remaining second optical carrier and two +1 order sidebands. In the simulation, 6 WDM channels each carrying 2.5 Gb/s downlink data have been up-converted to 15 GHz and 25 GHz microwave signals simultaneously, and 6 WDM channels each carrying 2.5 Gb/s uplink baseband data are sent to the central station. Both downlink and uplink transmission with less than 1 dB power penalty on average after 20 km SMF transmission. This full-duplex WDM-RoF system shows high spectral-efficiency, large communication capacity, simple cost-efficient configuration and good performance over long distance transmission.

Simultaneous MMW generation and up-conversion for WDM-ROF systems based on FP laser

A new wavelength division multiplexing radio-over-fiber (WDM-ROF) scheme based on Fabry-Perot (FP) laser is proposed and demonstrated for simultaneous millimeter-wave (MMW) generation and up-conversion. The tunable optical comb generated by FP laser is served as a cost-effective WDM optical source in central station (CS) and it makes all-optical up-conversion process for all channels simple compared with using a DFB array. All modes from the FP laser are modulated simultaneously by a LiNbO3 Mach-Zehnder modulator (LN-MZM) then. We have systematically compared the performances of MMW generation and up-conversion using LN-MZM based on different modulation schemes. A reflective semiconductor optical amplifiers (RSOA) is used both for the downstream modulation of each channel and for the reduction of mode partition noise (MPN) induced from FP laser. In the scheme, the multiple optical carrier suppression (OCS) modulation shows the highest receiver sensitivity and smallest power penalty over long-distance delivery. In the numerical simulation, 7 WDM channels each carrying 2.5Gb/s baseband signal have been up-converted to 60GHz simultaneously with good performance over 25km single mode fiber (SMF) transmission.

Optical up-conversion for WDM-RoF transmission using multiple optical carrier suppression in OFCG

A tunable optical frequency comb generator (OFCG) by cascading an Electro-absorption modulator (EAM) followed by a phase modulator (PM) and an intensity modulator (IM) is proposed for wavelength division multiplexing radio-over-fiber (WDM-RoF) transmission. The generated OFCG serves as the carriers of WDM-RoF system to realize all-optical up-conversion afterwards. In the proposal, each comb line is modulated by the radio-frequency (RF) signal via multiple optical carrier suppression (OCS) after optical comb generation. We have systematically compared the performances of the optical up-conversion based on different modulation schemes. Among three schemes, the OCS modulation scheme shows the highest receiver sensitivity and smallest power penalty over long-distance transmission. What's more, the OCS modulation scheme can be easily implemented with a large number of WDM channels simultaneously without any power saturation or other nonlinear impact. In the numerical simulation, 15 WDM channels each carrying 15Gb/s×5Gb/s baseband signal have been up-converted to 10GHz simultaneously. This method still provides high performance after 20km transmission, which shows simple cost-efficient configuration and good performance over long distance delivery.

A novel full duplex 16 Gbps SCM/ASK radio over fiber WDM-PON sharing wavelength for up- and down-link using bidirectional reflective filter

In this paper, a new bidirectional wavelength division multiplexing radio-over-fiber (WDM-RoF) using Subcarrier Multiplexing/Amplitude Shift Keying (SCM/ASK) is proposed which shares the same wavelengths for both up-link and down-link. A bidirectional reflective filter (BRF) is utilized in the upstream link to provide a reliable bidirectional optical channel. WDM is used to further increase the capacity of system. Simulation of the proposed scheme demonstrates 1Gbps down- and up-link data stream for 16 channels over the length of 25km with acceptable Q-factor (>6dB).

Novel full-duplex SSB WDM-RoF system with SLM technique for decreasing PAPR

A novel full-duplex single-sideband (SSB) wavelength division multiplexing radio over fiber (WDM-RoF) system with selected mapping (SLM) technique for decreasing peak-to-average power ratio (PAPR) is proposed in this paper. At the central office (CO), the generated SSB signal carrying 10 Gbit/s 16-ary quadrature amplitude modulation orthogonal frequency division multiplexing (16QAM-OFDM) downstream signal with SLM technique is sent to the base station, and 60 GHz SSB optical signal carrying 10 Gbit/s 16QAM-OFDM upstream signal is sent back to CO utilizing the wavelength-reuse technology. Simulation results show the proposed method for PAPR reduction can effectively improve the sensitivity of receiver, and the power penalty of the 16QAM-OFDM downlink (uplink) signal is about 2 dB (3 dB) at BER of 1×10−3 after 42 km standard single-mode fiber (SSMF) transmission.

High-Spectral-Efficiency Photonic Frequency Down-Conversion Using Optical Frequency Comb and SSB Modulation

A high-spectral-efficiency photonic frequency down-conversion approach for wavelength-division-multiplexing radio-over-fiber (WDM-ROF) uplinks is proposed and experimentally investigated. In the approach, an optical frequency comb serves as the carriers of multiple channels, and each comb line is modulated by the upstream radio-frequency (RF) signal via single-sideband modulation. At the central station, the beating between the sideband with upstream signal and its adjacent optical carrier leads to photonic frequency down-conversion without additional optical frequency shifts. Due to the band overlapping or the reduction of guard band between adjacent channels, a high spectral efficiency is achieved for WDM-ROF uplinks. A two-channel experimental uplink is established, where a 15-GHz RF signal carrying quadrature phase shift keying (QPSK) data is successfully down-converted to a 2-GHz intermediate frequency (IF) signal. For the 10-Mb/s QPSK data, the measured eye diagrams and the constellation diagrams clearly show the effectiveness of the frequency down-conversion and the influence of the transmission distance. In fact, the proposed approach is applied to the down-conversion at a high data rate up to several gigabits per second, such as a simulation demonstration at 2.5 Gb/s.

광결정 광섬유를 이용한 WDM-RoF 시스템의 채널간 전력변화 편차 분석

파장분할다중화-무선광통신(WDM-RoF) 시스템에서 광결정 광섬유를 이용하여 채널 간 고주파신호들의 전력변화의 편차를 분석하여 이들을 조절할 수 있음을 확인하였다. WDM-RoF 시스템의 경우, 원격노드에서의 고주파 신호 특성은 파장 의존성을 갖는 단일모드 광섬유의 분산 특성으로 인해 전송거리 증가에 대한 고주파신호 수신 전력 변화가 채널의 파장에 따른 편차를 나타내게 되며, 이는 전체 시스템 설계시 전송거리에 대한 제한 요소로 작용할 수 있다. 광결정 광섬유의 분산보상 특성을 이용하여 WDM 채널에 따른 고주파 전송특성을 개선할 수 있는 광결정 광섬유를 설계하고, 이를 통해 채널간 고주파 전송특성의 편차를 분석하였다. In this paper, we report that the differences between RF power levels can be improved in wavelength division multiplexing - radio over fiber (WDM-RoF) system by using a photonic crystal fiber. In a WDM-RoF system, each WDM channel experiences different received RF power level fluctuation in remote node (RN) because of wavelength-dependent dispersion. Since each WDM channel experiences different power fluctuation, the RF power fluctuation acts as a design constraint in viewpoint of network design. We designed a photonic crystal fiber to improve the effect of wavelength- dependent dispersion on RF power fluctuation. Also, we analyzed the wavelength-dependent difference of inter-channel RF power fluctuations.

Novel centralized-light-source WDM-RoF system with OFDM-CPM downstream and OOK upstream

In this paper, we have proposed and demonstrated a novel lightwave centralized wavelength division multiplexing radio-over-fiber (WDM-RoF) system employing OFDM-CPM generation and carrier-reuse technique. The 4×2.5-Gb/s OFDM-CPM wireless signal and upstream OOK signal are transmitted over 25km SMF-28 successfully. We further compare the OFDM-CPM signal with an OFDM-QPSK signal, and the experimental results suggest that OFDM-CPM modulation scheme will be a promising candidate for future WDM-RoF system.

광결정 광섬유를 갖는 WDM-ROF 시스템의 고주파 신호전송특성 분석

We analyze transmission performance of radio frequency signal in WDM-ROF (wavelength division multiplexing - radio over fiber) system employing photonic crystal fiber. In a WDM-ROF system employing conventional single-mode fiber, transmission performance of radio frequency signal is analyzed depending on each WDM channel. In this case, each WDM channel experiences power fluctuation of received RF signal in remote node because of double sidebands of the modulated signal and wavelength dependent dispersion of single mode fiber. This RF power fluctuation acts as a design constraint in viewpoint of system design. By employing photonic crystal fiber (PCF) with dispersion compensation characteristics, the transmission performance of RF signal can be improved compared with the case with SMF only.

Simultaneous Wired and Wireless 1.25-Gb/s Bidirectional WDM-RoF Transmission Using Multiple Optical Carrier Suppression in FP LD

In this paper, a new bidirectional wavelength division multiplexing radio-over-fiber (WDM-RoF) scheme is proposed with multiple optical carrier suppression for simultaneous wired and wireless 1.25-Gb/s signal transmission. For downstream signals, all modes of a Fabry-Perot laser diode are simultaneously suppressed by a Mach-Zehnder modulator at V pi bias point to mitigate a chromatic dispersion. A reflective SOA is used both for reduction of mode partition noise induced from the Fabry-Perot laser diode and for the downstream modulation of each channel. The effect of mode partition noise (MPN) reduction is verified by measuring radio frequency (RF) spectra and phase noises. For an upstream signal, another reflective semiconductor optical amplifier (RSOA) in base station (BS) is used by remodulation technique, which is verified by measuring both the RF spectra and a dynamic rage of an optical input power to the RSOA. A bit error rate (BER) of 10-11 for three downlink channels and one uplink channel at 1.25 Gb/s are experimentally demonstrated after 23-km SMF transmission.

Simultaneous all-optical frequency downconversion technique utilizing an SOA-MZI for WDM radio over fiber (RoF) applications

Simultaneous all-optical frequency-downconversion technique utilizing a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) is experimentally demonstrated, and its application to a wavelength-division-multiplexing (WDM) radio over fiber (RoF) uplink is proposed. The conversion efficiencies from 22.5 (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RF</sub> ) to 2.5 GHz (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IF</sub> =f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RF</sub> -2f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LO</sub> ) are in the range from 1.5 to 3 dB for the optical RF wavelength between 1548 and 1558 nm. Error-free simultaneous all-optical frequency downconversion of the two WDM RoF upstream channels that carry 155-Mb/s differential phase-shift keying data at 22.5 GHz to an optical intermediate frequency signal having the frequency of 2.5 GHz with the power penalty less than 0.1 dB at the bit error rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> is achieved