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An up/downstream shared optical beam forming network based on wavelength-swept for remote phased array antenna is presented and experimentally demonstrated. A shared optical true time delay (TTD) network minimizes the size and cost, which is made by 16 paths of variable lengths of dispersion compensation fibers splicing with single-mode fiber, and then corporate with optical circulators. The experimental results show that the proposed system provides wide bandwidth from 12 GHz to 17GHz. The main lobe is oriented from −49.3° to 45.9° and the spurious free dynamic range (SFDR) of 104.58 dB·Hz2/3 is achieved in this system. Besides, the optical beam forming network is not affected by external temperature interference. This structure could have applications in remote phased array antenna.

A photonics-assisted approach to dual-functional analog signal transmitter that can simultaneously generate radio-frequency (RF) signal and linear frequency modulation (LFM) signal is proposed and experimentally demonstrated. Two types of beat notes can be independently generated by heterodyning of two lasers in a photodiode using a 4-channel monolithic integrated distributed feedback (DFB) laser array. In this system, the frequency scanning for the analog signal is achieved by adding a saw-tooth signal modulating on DFB3. To the LFM signal, the center frequency and bandwidth can be tuned only by changing the direct current and the voltage of driving signal, respectively. In the experimental demonstration, the center frequency for the generated analog signal is ranging from 2 GHz to 35 GHz, limited only by the bandwidth of PD. The instantaneous bandwidth reaches to 10 GHz as well as the time-bandwidth product ~ 480,000 at the peak-to-peak voltage ~ 3.5 V. Dual-functional integration analog signal transmitter is possible to adapt to variable environments, with more flexible frequency tunability for multiple function and broadband bandwidth for high resolution.

Optical frequency comb (OFC), a periodic optical pulse train in time domain, has been widely employed to measure optical frequency due to its equidistant modes in the frequency domain. Here, we propose and demonstrate a novel optical spectrum analyzer for CW lasers based on stretching the OFC in a dispersive element and mapping the frequency comb into the time domain. The optical spectrum analyzer also provides instantaneous full-field (wavelength, amplitude and phase) optical characterization capability by combining with optical phase-diversity technology. Experimental results show that we successfully trace the evolution of modulated lasers with a measurement speed of ∼51 MHz (related to the pulse repetition of the OFC) and a high spectral resolution of ∼21 pm. Thanks to the use of wavelength-to-time mapping and OFC, the single channel measurement range of the proposed system can reach ∼10 nm, which breaks the restriction of the bandwidth of photodetector.

A dual-band optical self-interference cancellation (OSIC) system is proposed and experimentally demonstrated for in-band full-duplex (IBFD) system using a monolithic integrated multi-channel directly modulated laser (DML) array, tunable optical delay line (TODL) and optical variation attenuator (OVA), and photodetector. The key component of the OSIC system is the integrated DML array which is measured in terms of the spectral characteristic, P–I curve, and small-signal frequency response. The use of the integrated DML array can greatly save the cost as well as reduce the complexity and power consumption of the system. The proposed system is theoretically and experimentally verified. The theoretical analysis shows that the cancellation depth is associated with the attenuation ratio, the time delay and the microwave frequency of the RF signal. Experimentally, the cancellation depth is more than 43 dB in the frequency of 2.4 GHz and 5 GHz. For a broadband RF signal, cancellation depth of 25 dB is achieved with the bandwidth of ∼ 260 MHz at a center frequency of 2.4 GHz and 5 GHz. In addition, the switchability between double frequencies of the applied microwave signal makes the OSIC system more flexible and fast without adjusting the TODL and OVA, repeatedly

We report a monolithic integrated 4 × 25 Gb/s transmitter optical subassembly (TOSA) module at 1.55 μ m. The module consists of 4 directly modulated lasers (DMLs) and an arrayed waveguide grating (AWG) with 400 GHz channel spacing. The DMLs and AWG are highly integrated on a 4 mm × 6 mm InP chip which is mounted on an AlN substrate and butterfly packaged. The characteristic of the TOSA module is measured in terms of optical spectra, crosstalk and small-signal frequency response. Data transmission propagating over 3.1 km single mode fiber (SMF) at 25 Gb/s with non-return to zero on–off keying (NRZ-OOK) modulation is explored experimentally. The results show an excellent uniformity of the 4 DMLs, which all reaches 25 Gb/s. The transmission rate up to 100 Gb/s for back-to-back (BTB) and 3.1 km fiber transmission with an error rate of 10−9 is reached. Of great importance, the packaged 4 × 25 Gb/s TOSA module meets the ITU standards very well, showing a promising extension on more channels and higher transmission speed

A fast-switching single passband microwave photonic finite impulse response filter (MPF) using an incoherent broadband optical source (BOS) and an integrated spectrum shaper is proposed and experimentally demonstrated. The key component of our proposed MPF is the silica-on-silicon integrated spectrum shaper, which is used to slice the spectrum of the BOS. The performance of the integrated spectrum shaper is measured in terms of time delay, power consistency, and switching speed. A number of spectral shapes with the free spectrum range from 1.88 to 0.058 nm can be flexibly switched by changing the driving voltage of the optical switches. With the dispersion compensating fiber as dispersion medium, a fast-switching MPF with the switching speed up to 1.4-KHz is demonstrated in a wide tunable range from 1 to 12 GHz and the sidelobe suppression is up to 35 dB, which shows a great agreement with the theoretical result.

We propose a photonic scheme to realize a reconfigurable microwave photonic filter (MPF) with flexible tunability using a multi-wavelength laser (MWL) and a multi-channel phase-shifted fiber Bragg grating (PS-FBG). The proposed MPF is capable of performing reconfigurability including single bandpass filter, two independently bandpass filter and a flat-top bandpass filter. The performance such as the central frequency and the bandwidth of passband is tuned by controlling the wavelengths of the MWL. In the MPF, The light waves from a MWL are sent to a phase modulator (PM) to generate the phase-modulated optical signals. By applying a multi-channel PS-FBG, which has a series of narrow notches in the reflection spectrum with the free spectral range (FSR) of 0.8 nm, the +1 st sidebands are removed in the notches and the phased-modulated signals are converted to the intensity-modulated signals without beating signals generation between each two optical carriers. The proposed MPF is also experimentally verified. The 3-dB bandwidth of the MPF is broadened from 35 MHz to 135 MHz and the magnitude deviation of the top from the MPF is less than 0.2 dB within the frequency tunable range from 1 GHz to 5 GHz.

A fully characterization of an active optical filter based on an equivalent-phase-shifted DFB-SOA has been theoretically analyzed and experimentally demonstrated in this paper. By employing an optical vector network analyzer (OVNA), transmission characteristics of the equivalent-phase-shifted DFB-SOA are obtained. The influences of driven current on transmission characteristics of the equivalent-phase-shifted DFB-SOA are also investigated. In addition to the advantage of integration, the proposed equivalent-phase-shifted DFB-SOA also shows significant application in design of photonic devices for all-optical signal processing and computing.

A photonic-based true time delay (TTD) phased array antenna (PAA) with ultra-fast angle scan is proposed and experimentally demonstrated. A tunable TTD is realized using a wavelength-swept laser and an array of dispersive elements. The key novelty of our work is the ultra-fast angle scan using an ultra-fast wavelength-swept laser source, which is constructed by a gated multi-wavelength laser (MWL) and a dispersion compensation fiber (DCF). In our experiments, a wavelength-sweep time between two adjacent wavelengths is only several nanoseconds for wavelength spacing of 2.4, and 3.2 nm. We successfully realized an ultra-fast angle scan from 0 to 43° with a step of 8.8° in 12.48 ns.

A photonic-based phased array antenna (PAA) with ultra-fast beam scan is proposed and experimentally demonstrated using dispersion-based true time delay lines. The ultra-fast angle scan is realized using an ultra-fast wavelength-swept laser source which is constructed by a gated multi-wavelength laser (MWL) and a dispersion compensation fiber (DCF). The wavelength switching time is about several nanoseconds. In the results, we also successfully realized an ultra-fast angle scan from 0 to 43° within 12.48 ns.

We propose and experimentally demonstrate a photonic-assisted approach to microwave frequency measurement based on frequency-to-time mapping using a Fourier domain mode-locked optoelectronic oscillator (FDML OEO) operating around oscillation threshold. A relationship between the frequency of the unknown input microwave signals and the time difference of the output pulses is established with the help of the frequency scanning capability of the FDML OEO and, thus, can be used for microwave frequency measurement. The proposed scheme is characterized as having broad bandwidth, high resolution, multiple-frequency detection capability, and tunable measurement range. Microwave frequency measurement with a measurement range up to 16 GHz and a low measurement error of 0.07 GHz is realized.

Optoelectronic oscillators (OEOs) have been widely investigated to generate ultra-pure single-frequency microwave signals. Here, we propose and experimentally demonstrate a dual-chirp Fourier domain mode-locked (FDML) OEO to generate dual-chip microwave waveforms. In the proposed FDML OEO, a frequency-scanning dual-passband microwave photonics filter based on phase-modulation-to-intensity-modulation conversion using an optical notch filter and two laser diodes is incorporated into the OEO cavity. Fourier domain mode-locking operation is achieved by synchronizing the scanning period of the filter to the cavity round-trip time. Tunable dual-chirp microwave waveforms with a large time-bandwidth product are generated directly from the FDML OEO cavity in the experiment, which can be used in modern radar systems to improve its range-Doppler resolution.

To overcome the beam squint in wide instantaneous frequency, we review a number of system-level optical controlled phase array antennas for beam forming. The optical delay network based on a fiber device in terms of topological structure of an N-bit optical switch, fiber grating, high-dispersion fiber, and vector-sum technology is discussed, respectively. Lastly, an integrated circuit is simply summarized.

We propose a microwave photonics phase shifter which utilizes a coupling-modulated microring resonator (CMR) with interleaved p-n junctions. The transmission response of the CMR can be tuned by changing the effect coupling factor through applying bias voltage on the feedback arm. Finally, 1 V bias voltage is chosen to apply on the CMR. A microwave photonics phase shifter with phase shift range of 120 degree from 15 GHz to 40 GHz and the RF power variation less than 5 dBm is realized.

We propose and experimentally demonstrate an on-chip microwave phase shifter based on Coupling-modulated Microring Resonators (CMR). CMR is a structure that connected the transmission port and upload port of the normal ring resonator. In this case, the transmission spectrum can be tuned by properly adjusting the phase shift accumulation in the connected waveguide of the CMR. A deep notch of the transmission spectrum with 16 dB extinction ratio and 3-dB bandwidth of 17 GHz is chosen to achieve the phase shifter. And a phase shift ranging from 15 to 199 degree at 15 GHz with a radio-frequency power variation more than 7 dB is realized. After applying 1V voltage on the CMR, the extinction ratio changed to 5 dB. A quasi-linear phase shift range from 35 to 177 degree at 15 GHz with a radio-frequency power variation less than 2.5 dB is obtained. In addition, the characteristic of the phase shift at 20 GHz and 25 GHz is also tested and investigated. Moreover, this experiment indicates that the CMR has potential to solve the conflict between the large range of phase shift and small radio-frequency power variation in the ring resonator based phase shifter.

An X-band optically-steered phased array radar is developed to demonstrate high resolution multi-target detection. The beam forming is implemented based on wavelength-swept true time delay (TTD) technique. The beam forming system has a wide direction tuning range of ± 54 degree, low magnitude ripple of ± 0.5 dB and small delay error of 0.13 ps/nm. To further verify performance of the proposed optically-steered phased array radar, three experiments are then carried out to implement the single and multiple target detection. A linearly chirped X-band microwave signal is used as radar signal which is finally compressed at the receiver to improve the detection accuracy. The ranging resolution for multi-target detection is up to 2 cm within the measuring distance over 4 m and the azimuth angle error is less than 4 degree.

We experimentally demonstrate a broadband microwave photonics phase shifter. This phase shifter utilizes the free-carrier dispersion effect in a silicon microring resonator (MRR) with P-N junction. We characterize the phase and amplitude response of the MRR at different bias voltage. Experimental results show that a microwave photonics phase shifter with a bandwidth from 10 GHz to 15 GHz and a tuning range of 176 degree is realized by varying the bias voltage from 0.7 V to 0.9 V. The tuning speed of the microwave photonics phase shifter can be up to 1 ns according to the testing results of MRR.