Optical Radio Frequency Signal Research Articles

Theoretical Demonstration of Improved Performance in Multi-Channel Photonic RF Signals Based on Optical Injection Locking of Optical Comb and Array Lasers

Multi-channel radio frequency (RF) signal generation, facilitated by photonic technology, offers significant potential for generating coherent signals with a high frequency and low phase noise, providing multifunctional capabilities across diverse platforms, including RF and photonic systems. Traditional methods for multi-channel photonic RF signal generation typically entail the integration of diverse optical components, such as filters and amplifiers. However, this integration often results in compromises related to power efficiency, cost-effectiveness, and implementation simplicity. To address these challenges, we propose a novel method for generating multi-channel photonic RF signals based on optical injection locking technology. This approach eliminates the necessity for traditional optical components, leading to a substantial enhancement in the performance of photonic RF signals. We present the design of an optical injection locking-based multi-channel photonic RF signal generation schematic and theoretically evaluate its Signal-to-Noise Ratio (SNR) and eye pattern performance for data modulation using the Lumerical INTERCONNECT simulator. Our results reveal a significant 1.3-dB and 3.6-dB enhancement in SNR for 30-GHz and 60-GHz signals, respectively. Furthermore, we observed an improved communication performance, as evidenced by enhanced eye patterns in 3-Gbps data transmission compared to passive photonic RF signal generation methods.

Broadband photonic RF channelizer with 66 channels based on acousto-optic frequency shifter

Microwave photonic channelized receiver is one of the important means to realize broadband radio frequency (RF) signal reception, and it also has great application potential in the fields of radar systems and electronic warfare. In view of the above, a microwave photonic channelizer with 66-subchannels based on acousto-optic frequency shifter (AOFS) is proposed. The 11-line optical frequency comb (OFC) used in this scheme is generated via one phase modulator. The 33 optical local oscillators can be obtained using two AOFSs to shift the frequency of 11-line OFC up and down. The 33 optical local oscillators and broadband RF signal are image-rejected and downconverted in the I / Q receiver and output by 66 subchannels with a bandwidth of 500 MHz. The simulation results verify the complete reception of 3 to 36 GHz wideband RF signal, and the spurious-free dynamic range of the system can reach 116.3 dB · Hz2/3.

Photonic radio-frequency dissemination via optical fiber with high-phase stability.

We demonstrate a photonic radio-frequency transmission system via optical fiber. Optical radio-frequency signal is generated utilizing a Mach-Zehnder modulator based on double-side-band with carrier suppression modulation scheme. The phase error induced by optical fiber transmission is transferred to an intermediate frequency signal by the dual-heterodyne phase error transfer scheme, and then canceled by a phase locked loop. With precise phase compensation, a radio frequency with high-phase stability can be obtained at the remote end. We performed 20.07-GHz radio-frequency transfer over 100-km optical fiber, and achieved residual phase noise of -65 dBc/Hz at 1-Hz offset frequency, and the RMS timing jitter in the frequency range from 0.01 Hz to 1 MHz reaches 110 fs. The long-term frequency stability also achieves 8×10(-17) at 10,000 s averaging time.

Optical Radiofrequency Signal Mixing by All-Optical Sampling Based on a Semiconductor Optical Amplifier Mach–Zehnder Interferometer

Experimental performances analysis of an optical radiofrequency signal mixer based on a semiconductor optical amplifier Mach-Zehnder Interferometer utilizing an all-optical sampling method is presented. An optical pulse source generating 21-ps width pulses at a repetition rate of 7.8 GHz samples an intensity-modulated optical carrier carrying an electrical subcarrier at the intermediate frequency 1 GHz. The efficiency of the all-optical radiofrequency mixer is evaluated in terms of mixing conversion gain and third-order input intercept point. The conversion gain varies from 14.4 dB to 20.3 dB according to the chosen frequency. In addition, the electrical subcarrier modulated by a Quadrature phase shift keying (QPSK) and a 16-quadrature amplitude modulation (QAM) signal at a data rate of 1 MSymb/s has been frequency up-converted up to 40 GHz with an error vector magnitude of 11.68% for the QPSK modulation and 10.94% for the 16-QAM.

Conversion gain characterisation of optical radiofrequency signal mixing by all-optical sampling based on SOA-MZI

Using an optical network to transmit radiofrequency signals (radio over fibre) naturally leads to implementation functions, such as frequency mixing, directly in the optical layer. Proposed is an all-optical sampling method based on a SOA-MZI to frequency upconvert an electrical subcarrier at 1 GHz up to 38 GHz. The optical pulsed source used to sample the electrical subcarrier generates 21 ps-width pulses at a repetition rate of 7.8 GHz. Although the SOA-MZI bandwidth is limited to 7 GHz, frequency upconversions up to five times the 7.8 GHz sampling rate have been evaluated through the conversion gain. Its value lies between 14.4 to −20.3 dB depending on the frequency to be reached.

Experimental demonstration of tunable optical single sideband modulation and 1.5 Gb/s RoF downlink using stimulated Brillouin scattering

A frequency-tunable optical radio-frequency signal generation and broadband data upconversion technique with single sideband modulation for radio-over-fiber (RoF) systems is experimentally demonstrated. The proposed technique is based on optical processing an optical double sideband (DSB) modulated signal by using double stimulated Brillouin scattering interaction. On the one hand, a dual-electrode Mach–Zehnder modulator is used to realize broadband data upconversion. On the other hand, a fiber Bragg grating is applied to improve the optical carrier suppression ratio and avoid the effect of residual optical harmonics. By using this method, a broadband radio-frequency signal range from 5 to 40GHz with the undesired sideband suppression ratio over 58dB is experimentally demonstrated. In addition, the transmission performance of the 1.5Gb/s RoF downlink is also examined. The power penalty is less than 1dB at the bit-error rate of 10−10 after 50km single-mode fiber transmission.

Simultaneous generation of WDM RoF signals in an all-optical frequency upconverter utilizing a semiconductor optical amplifier

All-optical frequency upconversion utilizing a semiconductor optical amplifier (SOA) is experimentally demonstrated. Eight optical radiofrequency (RF) signals having the RF frequency of 26.5 GHz are simultaneously generated by four-wave mixing in the SOA. Power penalties for simultaneous generation of eight optical RF signals are less than 1.1 dB. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2420–2422, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27048

All-optical frequency upconversion of a quasi optical single sideband signal utilizing a nonlinear semiconductor optical amplifier for radio-over-fiber applications

An all-optical frequency upconversion technique using a quasi optical single sideband (q-OSSB) signal in a nonlinear semiconductor optical amplifier (NSOA) for radio-over-fiber applications is proposed and experimentally demonstrated. An optical radio frequency signal (f(RF) = 37.5 GHz) in the form of a q-OSSB signal is generated by mixing an optical intermediate frequency (IF) signal (f(IF) = 2.5 GHz) with an optical local oscillator signal (f(LO) = 35 GHz) utilizing coherent population oscillation and cross gain modulation effects in an NSOA. The phase noise, conversion efficiency, spurious free dynamic range (SFDR), and transmission characteristics of the q-OSSB signal are investigated.

Simultaneous WDM RoF Signal Generation Utilizing an All-Optical Frequency Upconverter Based on FWM in an SOA

A simultaneous all-optical frequency upconversion technique using four-wave mixing in a semiconductor optical amplifier (SOA) is experimentally demonstrated for wavelength-division-multiplexing (WDM) radio-over-fiber applications. Eight WDM optical radio-frequency (RF) signals having the RF frequency of 26.5 GHz are simultaneously generated by mixing eight WDM optical intermediate-frequency (IF) signals having the IF frequency of 2.5 GHz with an optical local oscillator signal of 24 GHz in a single SOA. The power penalty for simultaneous generation of eight WDM optical RF signals at the bit-error rate of 10-9 is less than 2.7 dB.

Optimisation of carrier-to-sideband ratio by triple-arm Mach–Zehnder modulators in radio-over-fibre links

A novel Mach–Zehnder modulation technique based on a 1×3 multimode interference coupler and three optical phase-modulator waveguides for the generation of optical single sideband (SSB) signals in the radio-over-fibre millimeter-wave system is proposed. Two of the three modulator arms are biased by the direct current (DC) voltage and modulated by the radio frequency (RF) signal in the same way as conventional SSB modulation method to produce optical RF signals, but the third one which can be named as ‘dc arm’ is only biased by DC to change the path of the optical carrier passing through it. The interference at the output of the triple-arm modulator happens at the optical carrier frequency, which makes the power of the optical carrier in the SSB signal controllable. Optimised modulation depth between the sideband component and the carrier of the generated SSB signal could be obtained by adjusting the bias voltage applied to the ‘dc arm’. It is proposed and analysed that the novel technique could improve the sensitivity of the optical receiver significantly compared with the conventional SSB modulation scheme.

Transmission of Wireless and Wired Services Employing a Simple System Architecture

This letter presents a novel modulation approach for simultaneous generation and transmission of optical radio-frequency (RF) wireless vector signal and baseband (BB) wireline signal using a single-electrode Mach-Zehnder modulator. Based on a double sideband with carrier suppression scheme and properly predistorted driving vector signal, a 2.5-Gb/s quadrature phase-shift keying (QPSK) signal at 60 GHz is generated with a 1.25-Gb/s BB ON-OFF-keying (OOK) signal. The proposed system can carry higher spectral efficiency vector signals and needs no optical filter to separate the BB and RF signals at remote nodes. Moreover, optical RF signal generation with frequency doubling is also achieved to reduce the bandwidth requirement of the transmitter. After transmission over 25-km single-mode fiber, the power penalties of the generated QPSK and OOK signals are about 4 and 0.1 dB, respectively.

BER and SFDR Characteristics of an FWM-Based All-Optical Frequency Upconverter

We have experimentally investigated the bit-error-rate (BER) and spurious-free dynamic range (SFDR) characteristics of an all-optical frequency upconverter based on the four-wave-mixing effect in a semiconductor optical amplifier for radio-over-fiber networks. The generation and error-free transmission of an optical radio-frequency signal having 155.52-Mb/s differential phase-shift keying data at a carrier frequency of 26.5 GHz are achieved. The dynamic ranges of an optical intermediate frequency (IF) input signal estimated from the BER and SFDR measurements are approximately 12 and 16 dB, respectively. The SFDR of the upconverter is larger than 77 dBmiddotHz2/3 for the IF frequencies ranging from 1 to 12 GHz.

Hybrid Access Network Integrated With Wireless Multilevel Vector and Wired Baseband Signals Using Frequency Doubling and No Optical Filtering

This letter experimentally demonstrated a hybrid access network which supports both radio-over-fiber and fiber-to-the-x systems. A 20-GHz radio-frequency (RF) 312.5-MSymbol/s M-ary phase-shift keying (PSK) signal and a baseband (BB) 1.25-Gb/s on-off keying signal are simultaneously generated and transmitted over an identical distributed infrastructure. The wired BB signal is compatible with the existing passive optical network (PON) system, and the wireless RF PSK signal can also share the same distributed infrastructure. The proposed system has no RF fading issue, no narrowband optical filter at remote node to separate the RF and BB signals, and can carry vector signals. Moreover, a frequency doubling for optical RF signal generation is achieved to reduce the bandwidth requirement of the transmitter. After transmission over 25-km standard signal-mode fiber, the receiver sensitivity penalties are less than 0.5 dB for both the RF and BB channels.

All-optical single-sideband upconversion with an optical interleaver and a semiconductor optical amplifier for radio-over-fiber applications

We propose and experimentally demonstrate an all-optical upconverter for the generation of an optical single-sideband (OSSB) signal in radio-over-fiber (RoF) systems. The OSSB signal, which is required for overcoming the fiber chromatic dispersion problem in RoF systems, is generated by using an all-optical SSB upconverter consisting of an optical interleaver and a semiconductor optical amplifier. With this upconversion technique, OSSB radio frequency (RF) signals with an RF frequency ranging from 15 GHz to 42.5 GHz are generated by mixing an optical intermediate frequency (IF) signal (1 GHz) with an optical local oscillator signal and transmitted over a 46 km standard single-mode fiber. The OSSB RF signal generated by this upconversion technique shows negligible dispersion-induced carrier suppression effects, which are usually observed for an optical double-sideband RF signal. The all-optical SSB upconverter provides high conversion efficiency of up to 29 dB and a sufficiently large spurious free dynamic range of 82 dB.Hz(2/3) for microcellular personal communication system applications.

A Novel Direct Detection Microwave Photonic Vector Modulation Scheme for Radio-Over-Fiber System

This letter demonstrates the feasibility of a novel direct detection microwave photonic vector modulation scheme for the radio-over-fiber (RoF) system. Unlike the traditional double-sideband with optical carrier suppression modulation scheme, which can carry only the on-off keying data format, the proposed scheme encodes the electrical vector signal on either the upper sideband (USB) or the lower sideband (LSB) only and a pure optical subcarrier on the other sideband. Therefore, phase and amplitude information will be preserved after direct detection. A frequency doubling scheme is employed to reduce the cost of RoF systems. Additionally, the relative intensity between USB and LSB can be easily tuned by adjusting the individual power of electrical driving signals to optimize the performance of the optical radio-frequency signals. A proof-of-concept experiment is conducted by using a 1.25 Gb/s BPSK signal at a carrier frequency of 20 GHz. After transmission over 50-km single-mode fiber, the receiver sensitivity penalty is less than 0.5 dB.

Error-free simultaneous all-optical upconversion of WDM radio-over-fiber signals

A simultaneous all-optical upconversion technique for cost-effective wavelength-division-multiplexing (WDM) radio-over-fiber (RoF) applications utilizing a semiconductor optical amplifier (SOA) Mach-Zehnder interferometer is investigated. The proposed upconversion scheme uses only one frequency upconverter for multi-RoF channels, thereby reducing the complexity and cost of the system. Error-free simultaneous all-optical upconversion of two WDM intermediate frequency (IF) channels (155-Mb/s differential phase-shift keying signal at 2.5 GHz) to an optical radio frequency signal (22.5 GHz) is achieved. In addition, the effect of gain saturation of the SOA due to the increased number of WDM IF channels on bit-error-rates performance is also experimentally investigated.