An optoelectronic oscillator (OEO) with wide tuning range and stabilized output is proposed and experimentally demonstrated. In the proposed OEO, a narrow-passband microwave photonic filter (MPF) is implemented by a joint operation of a dispersion-induced MPF, an infinite impulse response (IIR) filter based on a double-parallel recirculating delay line, and a two-tap finite impulse response (FIR) filter based on a polarization multiplexed dual-loop. By changing the time delay difference between the two polarization states of the polarization division multiplexing emulator within the dispersion-induced MPF, the central frequency of the narrow-passband MPF can be adjusted, and the tunability of the OEO is realized. A theoretical derivation is achieved, which is verified by an experiment. Tunable oscillation signals from 8.09 to 12.1 GHz at an average tuning step of ∼500 MHz are generated. With the help of the IIR and two-tap FIR filters, the strong stability and high side-mode suppression performance of the OEO is realized, where the maximum frequency drift of the generated 8.09 GHz signal is observed to be 2.1 kHz over 1 h and its side-mode suppression ratio reaches 61 dB with a frequency span of 5 MHz. The phase noise performance of the scheme is also studied.
A frequency-doubling optoelectronic oscillator with wideband frequency tunability implemented using a polarization modulator (PolM) and a phase-shifted fiber Bragg grating (PS-FBG) is proposed and experimentally demonstrated. In the proposed structure, the output from the PolM is divided into two branches by an optical coupler. In the lower branch, an optoelectronic feedback loop is formed in which a tunable microwave photonic filter (MPF) is constructed by the joint operation of the PolM, the PS-FBG, a tunable laser source (TLS), a polarization controller (PC), and a polarizer, the MPF serves as an oscillation mode selector that its central frequency is a function of the frequency difference between the TLS and the notch of the PS-FBG. In the upper branch, an equivalent Mach–Zehnder modulator (MZM) is performed by the joint use of the PolM, a second PC, and a second polarizer, the second PC is adjusted to let the bias point of the MZM located at the minimum transmission point (MITP), which generates an optical signal with two sidebands at the ±first orders. By beating the two sidebands at a second photodetector (PD), a frequency-doubled microwave signal is generated. By simply adjusting the wavelength of the TLS, the central frequency of the MPF is shifted, and the fundamental oscillation and its frequency-doubled signals can be tuned. The detailed theoretical study is achieved, and a verified experiment is established. A fundamental oscillation signal with a frequency tuning range from 9.39 to 15.4 GHz is generated in the OEO loop, which is multiplied to generate a tunable frequency-doubled signal. Their overall performances are also investigated.
This paper proposes a frequency-tunable optoelectronic oscillator (OEO) based on a single bandpass microwave photonic filter (MPF), which is implemented by a polarization division multiplexing emulator (PDME) with a tunable time delay difference between the two polarization states, a polarization modulator (PolM), a broadband optical source (BOS), and a linearly chirped fiber Bragg grating (LCFBG). The center frequency of the MPF can be shifted by adjusting the time delay difference between the two polarization states of the PDME. By incorporating the MPF into an OEO, the oscillation frequency of OEO is tuned. The proposed OEO is experimentally demonstrated. Frequency-tunable oscillation signals from 2.45 to 12.72 GHz are generated with their performance being investigated.
This paper proposes and demonstrates an optoelectronic oscillator (OEO) for the generation of a microwave signal with a wide frequency tuning range. In the proposed OEO, a microwave photonic filter (MPF) is formed by a joint operation of a dual-parallel Mach–Zehnder (DP-MZM) and a phase-shifted fiber Bragg grating (PS-FBG). The DP-MZM is employed to generate a modulated signal which includes an optical carrier and odd-order sidebands. The PS-FBG is used as an optical notch filter to remove the +1st sideband. Since the central frequency of the MPF can be shifted by changing the optical wavelength, the frequency tunability of the OEO is then realized by incorporating such an all-optical MPF into an optical domain dual-loop OEO without any electronic microwave filters. As a result, a microwave signal with a frequency-tuning range from 2.483 to 12.571 GHz is generated with its performance being evaluated.
An optoelectronic oscillator (OEO) for the generation of a frequency-doubled or -quadrupled microwave signal with a tunable frequency multiplication technique is proposed and demonstrated. In the proposed OEO, a modulated signal is generated by a Mach–Zehnder modulator (MZM). The modulated signal is then divided into two parts. One part is sent to a photodetector (PD1) via an optical domain dual-loop composite cavity and then fed back to the MZM to form the OEO loop that can generate an oscillation signal with the frequency determined by the center frequency of an electrical bandpass filter used in the loop and the length difference of the dual-loop composite cavity. The other part is sent to a fiber-optic recirculating delay line (RDL) structure and then applied to another PD (PD2) for the formation of a microwave photonic (MWP) notch filter. Through using the cascade characteristics of the RDL loop in the fiber-optic RDL structure and the notch response of the MWP notch filter, a frequency-doubled or -quadrupled microwave signal is generated. A detailed theoretical analysis is provided and the results are verified by an experiment. A fundamental oscillation signal at 5.592 GHz is generated in the OEO loop, which is multiplied to generate a frequency-doubled microwave signal at 11.184 GHz or a frequency-quadrupled microwave signal at 22.368 GHz, respectively. The performance of the generated microwave signals is also investigated.
A frequency-doubling optoelectronic oscillator (OEO) using two cascaded modulators based on destructive interference is proposed and experimentally demonstrated. In the proposed system, we utilize a cascaded modulator including a phase modulator and an intensity modulator, which implements a carrier-suppressed double-sideband modulation based on destructive interference to generate a frequency-doubled microwave signal. Meanwhile, the phase modulator is connected by a chirp fiber Bragg grating in the loop, which forms a microwave photonic filter to select the fundamental frequency signal in the OEO loop. As a result, a frequency-doubled microwave signal at 17.9 and 20.5 GHz is generated, respectively. The phase noises and the long-term stability of the generated microwave signals are also investigated.
A tunable optoelectronic oscillator (OEO), which employs an all-optical microwave photonic filter (MPF) consisting of two laser sources (LD1 and LD2), an optical coupler (OC, 50:50), a Mach-Zehnder modulator (MZM), and a chirped fiber Bragg grating, is proposed. Because the central frequency of the all-optical MPF can be shifted by changing the wavelength spacing between the two laser sources, the frequency tunability of the OEO can be realized by incorporating such an all-optical MPF into an optical domain dual-loop OEO without any electronic microwave filters. A detailed theoretical analysis is presented and the results are confirmed by an experiment. A microwave signal with a frequency-tuning range from 4.057 to 8.595 GHz is generated. The phase noise, the long-term stability, and the side-mode suppression performance of the generated microwave signal are also investigated.
A reconfigurable optoelectronic oscillator (OEO) based on a double-coupling recirculating delay line (DC-RDL) is analyzed and experimentally demonstrated. In the proposed OEO, an incoherent two-tap microwave photonic filter is formed by an amplified spontaneous emission (ASE) source, a Mach–Zehnder modulator, a DC-RDL, and a polarization beam splitter (PBS) to realize selection of the oscillation mode. Specifically, the incoherence is implemented using an ASE broadband laser source and a DC-RDL, and the high sidemode suppression performance can be achieved by employing the dual-loops system between the dual output of the DC-RDL and the PBS. A detailed theoretical analysis is provided and is verified by the experiment. The single-sideband phase noise, the frequency tunability, and the long-term stability of the generated microwave signal are investigated. In addition, the frequency independent of the phase noise is also experimentally observed.
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