A photonic-based approach for multifunctional microwave signal generation and processing is demonstrated based on equivalent phase modulation. The key component of the system is a dual-polarization quadrature phase-shift keying (DPQPSK) modulator. One dual-parallel Mach-Zehnder modulator (DP-MZM) in the DP-QPSK modulator is biased to function as an equivalent phase modulator (e-PM), while the other DP-MZM is biased as a carrier-suppressed singlesideband (CS-SSB) modulator. The two optical signals from the two DP-MZMs are combined and detected in a photodetector. With different driving signals applied to the two DP-MZMs, different functions can be achieved. When the e-PM is driven by a direct current signal to phase shift the optical carrier, and the CS-SSB modulator is to generate a first-order optical sideband of the driving RF signal, a wideband microwave phase shifter is implemented, which can introduce arbitrary phase shift to the electrical driven signal applied to the CS-SSB modulator. Under the above condition, if the CS-SSB modulator is to generator a first-order and an opposite third-order optical sidebands of the driving RF signal, a repetition rate tunable triangular and square waveform generation scheme can be realized. When the e-PM is driving by an electrical coding signal, and the CS-SSB modulator is to generate a first-order optical sideband of the driving RF signal, a reconfigurable pulse compression signal generator is achieved. Experimental verifications are made to demonstrate the multifunctional system, which has the potential to be used in a variety of microwave systems.
A photonic approach for simultaneous frequency down-conversion, self-interference cancellation, and image rejection for in-band full-duplex radio-over-fiber systems is proposed based on a dual-polarization quadrature phase-shift keying (DP-QPSK) modulator. The upper dual-parallel Mach–Zehnder modulator (DP-MZM) of the DP-QPSK modulator realizes the radio frequency (RF) self-interference cancellation and generates the upper and lower first-order optical sidebands of the desired RF signal, whereas the lower DP-MZM generates two optical sidebands of the local oscillator. The optical signals from the two DP-MZMs are combined, and the upper and lower optical sidebands are separated by a wavelength division multiplexer (WDM). The two outputs from the WDM are detected at two photodetectors for frequency down-conversion. By combining the two intermediate-frequency (IF) signals at a 90°hybrid coupler, the proposed system can also achieve image rejection. In addition, by changing the bias point of the lower DP-MZM, second-harmonic frequency down-conversion can be implemented. A simulation is performed. A QPSK-modulated RF signal from 5 to 44 GHz is successfully down-converted to 1-GHz IF signal with self-interference and image frequency cancelled, and the EVM of the received IF signal is lower than 15%.
KEYWORDS: Fiber Bragg gratings, Modulators, Modulation, Signal to noise ratio, Transmitters, Signal generators, Radio over Fiber, Radio optics, Signal attenuation, Signal detection
A photonic-assisted radio-frequency (RF) self-interference cancellation (SIC) scheme for in-band full-duplex radio-over-fiber system is proposed based on a dual-drive Mach–Zehnder modulator (DD-MZM) and a fiber Bragg grating (FBG). The received signal with an interference from the transmitter is applied to one arm of the DD-MZM, and the reference signal tapped from the transmitter is injected into another arm of the DD-MZM. By properly controlling the amplitude and phase of the reference signal, and adjusting the bias point of the DD-MZM, the RF interference can be cancelled in the optical domain. An FBG is used to convert the phase-modulated received signal to an intensity-modulated signal for information recovery. Since the self-interference is cancelled directly in the optical domain, the proposed SIC scheme is suitable for long-distance fiber transmission. A simulation is performed, where a cancellation depth of more than 50 dB is achieved. The proposed SIC system features good transmission capability and frequency tunability, which is only limited by the bandwidths of the DD-MZM and the FBG.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.