Optical Millimeter-wave Signal Research Articles

Scheme to eliminate the time shift of code edges based on the optimal transmission point of a DP-MZM.

To eliminate the time shift of code edges on a single-sideband (SSB) modulation signal transmission in a radio-over-fiber (RoF) system, a new, to the best of our knowledge, SSB modulation scheme based on an optimal transmission point for a double-parallel Mach-Zehnder modulator (DP-MZM) is proposed. The scheme is based on DP-MZM to realize the separation of the carrier and the +1st-order sideband at the optimal transmission point, and the baseband signal modulates the 2.5Gb/s data signal to the +1st-order sideband of the SSB signal; then, the carrier and the +1st-order sideband are transmitted with a carrier-to-sideband ratio of 0dB. Theoretical analysis shows that compared to the traditional SSB-modulated optical millimeter-wave signal generation scheme this scheme completely solves the problem of the time shift of code edges caused by dispersion. The simulation results show that the improved SSB modulation scheme has a Q factor of 23.362, the minimum bit error rate is 4.207×10-127 at 73.453km, and the eye diagram is still very clear. Under the premise of meeting the basic requirements of communications, the maximum communications distance can reach 135km, which is 270% of the transmission distance of a traditional SSB modulation model.Thus, the system performance has been greatly improved.

Effect of Phase Noise on the Optical Millimeter-Wave Signal in the DWDM-RoF System

In this study, we examined the effect of phase noise on the optical millimeter-wave (mm-wave) signal in a dense wavelength division multiplexing radio-over-fiber (DWDM-RoF) system. A single modulator was used to generate the optical mm-wave signal in the DWDM-RoF system. This paper addresses the impact of phase noise, which results from phase imbalance, on the optical mm-wave signal. To lower the effect of phase noise on the optical mm-wave signal, the phase imbalance should be controlled. The phase imbalance can be controlled and decreased by adjusting the phase at the phase shift (PS). The system performance was analyzed using various parameters such as bit error rate (BER), signal-to-noise ratio (SNR), optical signal to noise ratio (OSNR), and error vector magnitude (EVM). From the results, we found the phase imbalance affected the optical mm-wave signal due to the imbalanced splitting of the signal intensity at the MZM. The phase imbalance impacts the phase noise, which impacts the optical mm-wave signal. The phase noise could be decreased by controlling the phase imbalance at the phase of 5π/12. The best results at the phase of 5π/12 were collected for phase noise at 0.02 degrees.

Modulation Index and Phase Imbalance of Dual-Sideband Optical Carrier Suppression (DSB-OCS) in Optical Millimeter-Wave System

This paper presents a Dual-sideband Optical Carrier Suppression (DSB-OCS) technique which is used to generate an optical millimeter-wave (mm-wave) signal in radio over fiber (RoF) systems. The proposed system employs a Dual-Electrode Mach-Zehnder Modulator (DE-MZM) and a carrier of 40 GHz mm-wave for data transmission through the RoF systems. Characteristics determining the performance of the system, among which are the modulation index, phase imbalance and dispersion parameters, are included. The performance evaluations of the system show that the mm-wave signal output power follows MZM’s transfer function when the modulation index is raised. Moreover, the generated optical mm-wave signal power is affected by phase imbalance and optical splitting ratio. It is observed that the optical fiber dispersion influences the DSB-OCS system by decreasing the amplitude of the mm-wave and the signal-to-noise ratio (SNR).

Optical Milli-Meter Wave Signal Generation using Frequency Octupling Without Optical Filter

In this paper, we show a practical technique to produce a great octupledfrequency optical Millimeter-Wave (MMW) signal utilizing two Mach-Zehnder modulators associated in course. A Continuous Wave (CW) Laser, two LiNb Mach-Zehnder Modulators(MZM) and a PIN Photodiode are utilized in the MMW signal age A careful change of Direct Current (DC) inclination, tweak index(MI) and the presentation of a 90° stage move between the 2 fell stages guarantees the age of recurrence octupled MMW signal.80 GHz RF signal is produced from a 10 GHz RF Local Oscillator (LO) with a most extreme reachable with Optical Sideband Suppression Ratio (OSSR) of 57 dB and a Radio Frequency Spurious Suppression Ratio (RFSSR) of beyond what 42 dB can be gotten. An optical bearer is tweaked, and unadulterated ±fourth-request sidebands are produced. The whole connection is reproduced utilizing Optisystem Software.

8 phase-shift-keying optical millimeter-wave signal generation by electro-optical phase modulator-based photonic frequency quintupling

We have proposed an 8 phase-shift-keying (PSK) optical millimeter-wave (MMW) signal generation scheme with frequency quintupling enabled by an electro-optical phase modulator (PM) and a wavelength selective switch. In this scheme, the radio frequency (RF) carrier with 8PSK signal is modulated on the lightwave via the PM with simple precoding but constant Euclidean distance, and is recovered to the original 8PSK signal with the frequency-quintupling RF carrier based on the phase periodicity of an 8PSK signal. By optimizing the voltage amplitude of the 8PSK RF driving signal, the generated frequency-quintupled 8PSK MMW signal is maximized at a given laser launch power. A radio over fiber simulation link is built to demonstrate the theoretical analysis. The simulated constellations and bit-error-rate curves show that the frequency-quintupling 8PSK MMW signal has good transmission performance. The simulation results agree well with our theoretical prediction.

All optical Millimeter-wave signal generation and transmission for radio over fiber (RoF) link

<span>Fiber-based wireless system has become a promising solution as a cost- effective communication and it offers high capacity network with millimeter- wave (mm-wave) signal transmission. The system significantly offers superior possible bandwidths for both fiber and free-space applications. Hence, with the increased capacity as well as wireless mobile network applications particularly at mm-wave signal, radio over fiber (RoF) technology is the utmost option. Nevertheless, when high frequency signal transmission is involved, power fading or dispersion effect limits the performance of RoF link. Therefore, this work proposed a RoF system by integrating remote optical local oscillator (LO) with frequency up-conversion at the base station (BS). All optical mm-wave signals are generated and transmitted for the RoF link. The effects of the changes of fiber loop length, optical power of the continuous wave (CW) optical laser carrier and responsivity value of the p-i-n photodiode (PD) mainly at 40 GHz are investigated and the power fading effects are discussed.</span>

Full-duplex mobile fronthaul link for low- and high-frequency hybrid network architecture with colorless RRU based on analog radio over fiber technology

Full-duplex mobile fronthaul (MFH) architecture with a colorless remote radio unit (RRU) and further RRU (F-RRU) based on radio over fiber technology (F-RRU) is proposed. Such MFH architecture can carry out low- and high-frequency hybrid networking for common seamless wide coverage and high data rate requirements in hotspot areas. Optical millimeter-wave signal is abstracted by an interleaver in the RRU and then is transmitted to multiple F-RRUs. The polarization multiplexing technology and power splitters employed make the RRU and F-RRU free from the laser sources, as the uplink optical carrier is abstracted from the downlink. Simulations are conducted to demonstrate the reliability of the proposed MFH architecture, and results show that the radio signals maintain strong performance after standard single mode fiber transmission.

Optical millimeter wave generation utilizing stimulated brillouin scattering for radio over fiber system

<span>Optical millimeter-wave signal generation in Radio over Fiber (RoF) based on external modulators using different modulation schemes such as Single-Sideband (SSB), Double-Sideband (DSB) are experimentally compared. The major fallout for external modulation scheme system performance to downgrade is due to dispersion and the fading effect in optical signal generation while generating high Bit Error Rate (BER) when involving long distance delivery. In this work, we proposed mm-wave signal utilize Stimulated Brillouin Scattering (SBS) scheme which indicates the best performance amongst the scheme based on simulation that it achieves to propagate longest of distance over fiber, highest receiver sensitivity, the lowest BER and coherence of Mach-Zehnder Modulator (MZM) extinction ratio. Mm-wave signal of 40 Ghz and 10 Gb/s data rate was generated with the plotting of eye diagram.</span>

Radio-over-fiber system with octuple frequency optical millimeter-wave signal generation using dual-parallel Mach–Zehnder modulator based on four-wave mixing in semiconductor optical amplifier

We have proposed a scheme of radio-over-fiber (RoF) system employing a dual-parallel Mach–Zehnder modulator (DP-MZM) based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). In this scheme, the pump and the signal are generated by properly adjusting the direct current bias, modulation index of the DP-MZM, and the phase difference between the sub-MZMs. Because of the pump and the signal deriving from the same optical wave, the polarization states of the two lightwaves are copolarized. The single-pump FWM is polarization insensitive. After FWM and optical filtering, the optical millimeter-wave with octuple frequency is generated. About 40-GHz RoF system with a 2.5-Gbit / s signal is implemented by numerical simulation; the result shows that it has a good performance after the signal is transmitted over 40-km single-mode fiber. Then, the effects of the SOA’s injection current and the carrier-to-sideband ratio on the system performance are discussed by simulation, and the optimum value for the system is obtained.

Generation of Multiple-Frequency Optical Millimeter-Wave Signal With Optical Carrier Suppression and No Optical Filter

We propose and experimentally demonstrate the generation of a multiple-frequency optical millimeter-wave (mm-wave) signal an without optical filter at the transmitter side. Forty, 80, and 120-GHz multiple-frequency optical mm-wave signals are generated simultaneously in our experiment. After 20 km standard single-mode fiber transmission, high-quality eye diagrams with large opening and high stability are obtained at these frequency bands.

Dual-Tone QPSK Optical Millimeter-Wave Signal Generation by Frequency Nonupling the RF Signal Without Phase Precoding

A novel dual-tone quadrature phase-shift keying (QPSK) optical millimeter (mm)-wave signal generation by frequency nonupling the radio-frequency QPSK signal via an optical phase modulator (PM) without phase precoding is proposed. To enable the generated optical mm-wave signal to resist the fiber chromatic dispersion degradation, the unmodulated −fourth-order and the QPSK-modulated +fifth-order sidebands are abstracted from the generated sidebands, considering the phase periodicity of a QPSK signal. The opto-electrical conversion efficiency is maximized by optimizing the modulation index of PM. An optical mm-wave generator along with a radio-over-fiber link is built, and the eye diagrams, constellations, and BER curves demonstrate that the frequency nonupling dual-tone QPSK optical mm-wave signal performs well. The simulated results agree well with the theoretical prediction.

BPSK optical mm-wave signal generation by septupling frequency via a single optical phase modulator

In this paper, we have proposed a novel and simple scheme to generate the BPSK optical millimeter wave (MMW) signal with frequency septupling by using an optical phase modulator (PM) and a wavelength selective switch (WSS). In this scheme, the PM is driven by a radio frequency (RF) BPSK signal at the optimized modulation index of 4.89 to assure the 4th and 3rd-order sidebands have equal amplitudes. An wavelength selective switch (WSS) is used to abstract the −4th and +3rd-order sidebands from the spectrum generated by RF BPSK signal modulating the lightwave to form the BPSK optical MMW signal with frequency septupling the driving RF signal. In these two tones, only the +3rd-order sideband bears the BPSK signal while the −4th-order sideband is unmodulated since the phase information is canceled by the even times multiplication of the phase of BPSK signal. The MMW signal can avoid the pulse walk-off effect and the amplitude fading effect caused by the fiber chromatic dispersion. By adjusting the modulation index to assure the two tones have equal amplitude, the generated optical MMW signal has the maximal opto-electrical conversion efficiency and good transmission performance.

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

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.

A multi-band access radio-over-fiber link with SSB optical millimeter-wave signals based on optical carrier suppression modulation

In this paper, we have reported a radio-over-fiber (RoF) link with a single sideband (SSB) optical millimeter (mm)-wave signal to support the 20GHz, 40GHz and 60GHz mm-wave multiband wireless accesses, based on the optical carrier suppression (OCS) modulation via a nested Mach–Zehnder modulator (MZM). The downstream data is only modulated on one of the multiple tones of the optical signal. At the base station (BS), according to the requirement of the wireless users, the multitone optical signal can be decomposed as different SSB optical signals using tunable fiber Bragg gratings (FBGs). Each SSB optical signal consists of two tones: the data-bearing optical tone and a referenced optical local oscillator to convert the baseband optical signal to the electrical mm-wave one based on heterodyne beating. The simulation results reveal that our proposed scheme can provide multiband wireless accesses and without dispersion compensation after 30km single-mode fiber (SMF), the 10Gb/s 4-QAM downstream data on the three-band mm-waves have minor degradation.

An optical millimeter-wave generation scheme based on two parallel dual-parallel Mach–Zehnder modulators and polarization multiplexing

A novel filterless optical millimeter-wave signal generation scheme is proposed. In the scheme, the undesired sidebands are suppressed using two parallel dual-parallel Mach–Zehnder modulators (MZMs) with different modulation indexes and polarization multiplexing, and frequency multiplication factor as high as 16 can be achieved. Simulation results show that 80, 120, and 160 GHz signals are generated through a 10 GHz RF signal using the proposed method, and the performance of the generated signals is good when commercially available MZMs with extinction ratio of 20–30 dB are used. The scheme has large tunability of modulation index for frequency octupling and 12-tupling signals generation and high stability against the RF driving voltage deviation for frequency 16-tupling generation.

Full-duplex fiber-wireless link for alternative wired and 40-GHz band wireless access based on differential quaternary phase-shift optical single sideband millimeter-wave signal

A full-duplex fiber-wireless link with a uniform single sideband differential quaternary phase-shift keying optical millimeter-wave signal is proposed to provide wired or 40-GHz band wireless access alternatively. The uniform optical millimeter-wave signal that supports services for wired or wireless users is produced via an LiNbO3 Mach-Zehnder modulator. After being transmitted to the hybrid optical network unit (HONU), it can be demodulated in different patterns on the demand of the user terminals for wired or wireless access. Simultaneously, part of the blank optical carrier abstracted from it is reused as the uplink optical carrier, so the HONU is free from the laser source, and thus, the complexity and cost of the system are reduced. Moreover, since the two tones of the dual-tone optical millimeter wave come from the same source, they maintain high coherency even after being transmitted over fiber. Additionally, the downlink data are carried by one tone of the dual-tone optical millimeter wave, so the downlink optical millimeter-wave signal suffers little from the fiber chromatic dispersion and laser phase noise. The theoretical analysis and simulation results show that our proposed full-duplex link for alternative wired and wireless access maintains good performance even when the transmission link with standard single mode fiber is extended to 30 km.

Compensation of chromatic-dispersion for full-duplex radio-over-fiber links with vector signal transmission using frequency tripling

This paper demonstrates the theory of chromatic dispersion (CD)-induced constellation rotation (CR) in a radio-over-fiber (ROF) link, and a symmetry theory for compensation. A 60 GHz full-duplex ROF system with vector signal transmission using frequency-tripling modulation (FTM) is also proposed. The simulations for both 5 Gbps and 200 Mbps 16 QAM signal transmission show that the CD-induced CR can be entirely overcome due to the proposed method, and the proposed ROF schedule still maintains good performance even after 500 km of 200 Mbps vector signal transmission. Meanwhile, the central station is significantly simplified and cost-effective since only one 15 GHz local oscillator is needed for both the generation of an optical millimeter-wave signal and the carrier of the downlink intermediate-frequency (IF) signal.

High-power optical millimeter-wave signal generation with tunable frequency multiplication factor

This work demonstrates a simple and novel scheme for millimeter-wave (MMW) signal generation using optical multi-sidebands (OMSB) modulation. In the proposed methods, several pairs of optical sidebands can be generated by employing parallel phase modulators driven by a low frequency radio frequency (RF) signal. The optical sidebands will beat at a photodetector (PD) to generate high frequency MMW signal with tunable frequency multiplication factor, such as frequency octupling, 12-tupling, 16-tupling and 18-tupling. Since no optical filters or DC bias are used, the MMW signal has the evident character of high-power output. A generalized analytic expression and simulation verification for generating the frequency multi-tupling MMW signal are developed. The influences caused by non-ideal factors are discussed in detail, and undesired power ratios versus non-ideal factors are plotted and analyzed.

A High Speed Radio on Fiber Based on Optical Double-Sidebands via Optical Filter and Optical Phase Modulation

We demonstrate a system scheme of generating and transmitting base-band and radio frequency signal based on optical double-sidebands scheme to generate optical millimeter-wave signal via optical phase modulation (OPM) and FBG. The system architecture with the source of laser at central station, the data re-modulation on downlink optical carrier gained from one base station is a good method to reduce the cost of uplink transmitter, for it does not needs the source of laser and wavelength administration at the base station. The optical phase modulator is inexpensive and mature. The downlink communicated bandwidth can be doubled to realize Ultra Width Band & Ultra High Frequency (UHF) communication via phase modulation and FBG at the base station. And the other signal which is reflected by FBG can be reused as uplink via amplitude modulation availably. The simulation results show that the bi-directional 2.5Gbit/s data and UHF microwave with 24GHz is successfully transmitted over 50km distance of a single-mode optical fiber with a optical dispersion of 20ps/(nm·km), an optical attenuation of 0.25dB/km and a light source power of 3dBm.

A scalable and continuous-upgradable optical wireless and wired convergent access network.

In this work, a scalable and continuous upgradable convergent optical access network is proposed. By using a multi-wavelength coherent comb source and a programmable waveshaper at the central office (CO), optical millimeter-wave (mm-wave) signals of different frequencies (from baseband to > 100 GHz) can be generated. Hence, it provides a scalable and continuous upgradable solution for end-user who needs 60 GHz wireless services now and > 100 GHz wireless services in the future. During the upgrade, user only needs to upgrade their optical networking unit (ONU). A programmable waveshaper is used to select the suitable optical tones with wavelength separation equals to the desired mm-wave frequency; while the CO remains intact. The centralized characteristics of the proposed system can easily add any new service and end-user. The centralized control of the wavelength makes the system more stable. Wired data rate of 17.45 Gb/s and w-band wireless data rate up to 3.36 Gb/s were demonstrated after transmission over 40 km of single-mode fiber (SMF).