Large Spurious Free Dynamic Range Research Articles

High-Performance Microwave Photonic Transmission Enabled by an Adapter for Fundamental Mode in MMFs

Microwave photonic links (MPLs) have long been considered as an excellent way for radio frequency (RF) transmission due to their advantages such as light weight, high bandwidth, low cost and large spurious-free dynamic range (SFDR). However, the effective mode-field area (Aeff) of the single-mode fiber (SMF) used in the traditional MPL is not large, so the MPL based on SMF have relatively strong nonlinearity, which limits the processing power of SMFs to a level of few milliwatts. Few-mode fibers (FMFs) have been applied in MPL as an alternative due to the larger Aeff, and photonic lanterns are used simultaneously to excite the high-order mode of FMFs for RF signal transmission. However, the photonic lantern could bring additional insertion loss, and the production cost of FMFs is high, so we propose an MPL based on multimode fibers (MMFs) with mode field adapters (MFAs). Since MMFs have larger Aeff, the nonlinearity of the link can be greatly reduced. And matched MFAs realized by reverse tapering, to excite only the fundamental mode in MMFs to reduce the crosstalk, which are very stable. As a result, the stimulated Brillouin scattering threshold and SFDR are improved by 5 dB and 14.5 dB, respectively.

Silicon integrated frequency‐tunable microwave photonic bandpass filter

AbstractMicrowave photonic filters have been regarded as an alternative to traditional radio‐frequency filters because of their wide bandwidth and large tunability. Integrated microwave photonic filters can integrate all necessary components into a single chip and are highly demanded for future radio‐frequency applications. Here, a highly integrated frequency‐tunable microwave photonic bandpass filter based on a silicon platform is proposed and demonstrated. The integrated filter consists of a phase modulator, four cascaded microring resonators and a photodetector. The frequency‐tunable range of the integrated filter is from 6.1 to 35.9 GHz, and the reconfigurable bandwidth is from 0.22 to 0.54 GHz. A large spurious free dynamic range of 102.1 dB Hz2/3 is obtained. This highly integrated approach holds great promise for miniaturised, flexible, and high‐performance microwave signal processing in modern radar and communication systems.

Bidirectional colorless WDM-PON RoF system with large spurious free dynamic range

A bidirectional colorless wavelength-division-multiplexed passive optical network radio over fiber system with a large spurious-free dynamic range (SFDR) is proposed. By separating the unmodulated optical carrier from the polarization multiplexed optical signal in the optical network unit, upstream wavelength reuse is realized. By adjusting the angle and phase difference between the orthogonal optical polarization modes, third-order intermodulation distortion (IMD3) suppression of the downstream link is realized. The periodic power fading caused by dispersion in the system is solved through single sideband modulation. Experiments have verified the wavelength reuse effect of the upstream link. Compared with the traditional link based on a Mach–Zehnder modulator, the periodic power fading of the system is suppressed under different radio frequencies (RFs) and fiber lengths. The IMD3 of the downstream link is suppressed, and the SFDR is improved by more than 17 dB. Also, the proposed system is tested with a 16 quadrature amplitude modulation RF signal in the experiment, where a good adjacent channel power ratio and error vector magnitude of the system are obtained.

High Linearity Microwave Photonic Up-Conversion System Based on Parallel Dual-Drive Mach–Zehnder Modulators

A large dynamic frequency up-conversion scheme based on parallel dual-drive Mach–Zehnder modulators (DD-MZM) and balance detection is proposed and demonstrated experimentally. By optimizing the distribution ratio of the optical carrier power and the IF signal power between the two DD-MZMs, the third-order intermodulation components in two sub-links cancel each other upon the balanced photodetector. The measured results show that the large spurious-free dynamic range of 112.3 dB·Hz4/5 is obtained for an intermediate frequency signal of 2 GHz up-converted to 18 GHz, which is a 14.8 dB enhancement compared with the traditional carrier suppression double-sideband modulation mixer. The frequency up-conversion performance of the established system for the broadband signal is measured with the results demonstrating the feasibility of the proposed optimization scheme.

Integrated Microwave Photonic Spectral Shaping For Linearization and Spurious-Free Dynamic Range Enhancement

Integrated microwave photonics (MWP) is a fast growing area where high frequency microwave signals are processed in the optical domain, merging key advantages of both microwave photonics and photonic integrated circuits (PICs) technologies including low-loss, reconfigurability, advanced functionality, enhanced stability, and reduced footprint. Plenty of functionalities have been demonstrated in integrated MWP, especially based on spectral shaping technique, where the phase and amplitude of the optical spectrum is precisely tailored by PICs. However, on-chip linearization is lagging behind and has not been investigated deeply. It is crucial and urgent to study on-chip linearization methods, which will lead to advanced integrated MWP systems with large spurious-free dynamic range (SFDR). In this paper, we present two novel techniques for on-chip linearization of microwave photonic links. The first technique is based on line-by-line complex spectral shaping using a series of ring resonators. The second technique relies on spatial separation to achieve parallel spectral shaping in two complementary spatial channels. Both methods are demonstrated in low-loss programmable silicon nitride circuits that can already host a number of advanced functionalities. Our results point to the great potential of integrating advanced functionalities and linearization in the same integrated platform.

Wideband Dual-Channel Photonic RF Repeater Based on Polarization Division Multiplexing Modulation and Polarization Control

Radio frequency (RF) repeaters are often used in satellite communication, wireless wideband communication, and electronic warfare systems for signal receiving, forwarding, and processing. Due to frequency-dependent microwave devices, conventional electrical RF repeaters have limited bandwidth and are susceptible to electromagnetic interference. In this article, a dual-channel photonic RF repeater using a polarization-division multiplexing dual-parallel Mach–Zehnder modulator is proposed. The RF repeater is built entirely using optical methods and does not require any frequency-dependent equipment, thus enabling high operating frequency and large operating bandwidth. The modulator is used to perform frequency conversion on the received uplink/downlink RF signals, and the followed polarization controller and the balanced photodetector realize switching of the uplink and downlink RF channels. In the experiment, wide operating bandwidth (1–20 GHz), low channel crosstalk (>33 dB), and a large spurious-free dynamic range (106 dB·Hz2/3) for the RF repeater are obtained. Also, the channel switching of 16 quadrature amplitude modulation (QAM) RF signals with 200 Mbps data rate is demonstrated, while the adjacent channel power ratio (ACPR), demodulated constellation diagrams, and the error vector magnitude (EVM) are evaluated.

Fundamental/Subharmonic Photonic Microwave I/Q Up-Converter for Single Sideband and Vector Signal Generation

Microwave I/Q up-converter is widely used in modern electronic systems to achieve single-sideband (SSB) up-conversion and vector modulation. However, due to the frequency-dependent mixer and quadrature coupler, conventional electronic I/Q up-converters suffer limited operating bandwidth. In this paper, a photonic microwave I/Q up-converter is proposed using a polarization-division multiplexing modulator. The I/Q up-conversion channels are built in all-optical methods without any frequency-dependent devices, so a wide operating bandwidth is obtained. Balanced detection is also realized to reduce the noise figure. In the experiment, SSB signals with wide operating bandwidth (14–40 GHz), high sideband and carrier suppression (>20 dB), and large spurious-free dynamic range (110.4 Hz2/3) are generated. 16 and 64 quadrature amplitude modulation vector signals with data rates of 400 and 600 Mb/s at 40-GHz carrier frequency are also demonstrated. Furthermore, subharmonic I/Q up-conversion with similar performance is also realized using the same structure, which can well reduce the frequency requirement of the local oscillator signal and the drive circuits.

Simple frequency up-conversion based on nonlinear photodetection scheme of PD in direct modulation radio over fiber system

Abstract This paper presents a simple photonic frequency up-conversion system based on direct modulation radio over fiber (RoF) link which employs optical-microwave double-mixing scheme with a high-speed photodetector (PD). With this up-conversion technique, an intermediate frequency (IF) signal of 500 MHz carrying 40 Mbps 16-quadrature-amplitude-modulation (16-QAM) vector signal is up-converted to 16 GHz in a remote antenna unit via 25-km standard single-mode fiber (SMF) transmission. The received 16 GHz radio frequency (RF) signal is demodulated successfully with the error vector magnitude (EVM) of 7.5% rms. The direct modulation up-converting system provides a sufficiently large spurious free dynamic range of 90 dB·Hz 2/3 . The proposed architecture exhibits the advantages of cost-efficiency, system operation efficiency and reliability.

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.