Signal to noise ratio (SNR) is one of the key parameters in the communication, radar and spectrum perception systems. In this paper, we propose and demonstrate a SNR enhancement receiver with wide processing bandwidth and tunability, where two coherent optical frequency combs (OFCs) based on multi-channel microwave source and electro-optic modulators are incorporated to accomplish simultaneous frequency down-conversion and channelization. By exploiting a dual frequency microwave source as a comb driver, the FSR tunable OFC is demonstrated. The FSR of the laser can be tuned flexibly from 8 GHz to 12 GHz by controlling the controlling the frequency of the microwave source. Multifrequency microwave signal is generated from a 0-10GHz microwave signal source and cloned to the optical domain by a carrier suppressed single sideband modulator (CS-SS) and then down-converted and channelized to the same IF. The IF signals are digitalized and then added in the digital domain. With the proposed receiver a 7.2 dB SNR enhancement has been achieved.
In this paper, we illustrate a radio-frequency (RF) channelization scheme based on dual optical frequency combs (OFCs). Modulated by two sets of cascaded electro-optic (EO) modulators, dual coherent OFCs with different free spectrum ranges (FSRs), namely 10 GHz and 11 GHz, are generated. Based on OFCs, a channelizer with six channels, 1 GHz channel spacing is experimentally demonstrated, covering frequency range from 1 GHz to 7 GHz. The input RF signal is impressed onto the signal comb by a Dual-Parallel Mach-Zander modulator (DPMZM). At the same time, balance detection methods and I/Q demodulation are used to achieve high-precision reception and the processing of RF signals. Selecting the corresponding channel with a waveshaper, the performance of six channels is shown and the spectra at different stages are also demonstrated.
The optical filters are studied according to the applications of photonic-assisted radio frequency (RF) signal gereration and all optical coherent signal processing. Firstly, the finite impulse response (FIR) filter is analyzed theoretically. And it points out that the advantages of FIR lies in the reconfiguration, real coefficients and linear-phase impulse response which could guarantee the coherence of the ultrashort pulse. Based on this, the specific filters for free spectral range (FSR) broadening and sinusoidal signal generation are designed and simulated. The results of the simulation showed that the FSR of comb filter is 20 GHz with a sidelobe suppression of 20 dB, the demand of FSR broadening is satisfied. Meanwhile, based on the FSP stacking over several ten nanometre optical spectrum, shaping filter is realized for sinusoidal signal generation. Finally, the potentials of low dimensional materials enhanced integrated filters for wide FSR (< 50 nm) are discussed in the last part.
Broadband radio frequency signal generation based on ultrafast optical pulse shaping, which is a typical microwave photonic technology, has been performed. The ultrafast optical pulse starts from our home-made mode-locked laser which has a repetition rate of ~171 MHz and spans from 1524 nm to 1593 nm. Following the MLL is an optical amplifier which makes up for the loss of the photonic link. A commercial pulse shaper is introduced to flatten and shape the spectrum of the optical pulse. However, it results in a additionally frequency cutoff. Only the C-band (5 THz optical bandwidth) is used efficiently which results in waste of spectrum resources. Then, the shaped pulses travel through a 5km long optical fiber realizing frequency-to-time mapping. The RF signal is acquired from the optical intensity profile by a high-speed photodetector at last. Several different kinds of wideband RF signals are generalized from the same hardware system, such as trigonometric and linear frequency-chirped waveform from 2 GHz up to 3 GHz, These results may be of interest to the radar and communication systems with ultraband RF signals.
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.