Dual-loop diode-tuned Fourier domain harmonically mode-locked opto-electronic oscillator with over 50 dB side-mode spur reduction

Abstract

We propose and demonstrate a dual-loop harmonic Fourier domain mode-locked optoelectronic oscillator (FDML-OEO) for drastically reducing the side-mode spurs. The frequency domain mode-locking is achieved by synchronizing the scanning period of the filter to an integer fraction of the round trip times of the two loops with a self-made low cost diode-tuned RF filter. We found, for the first time to the best of authors’ knowledge, that the frequency scanning bandwidth (FSBW) of the mode-locked output is strongly affected by the length mismatch between the two fiber loops. By using the phase noise of FDML OEO’s delayed self-heterodyne signal as a performance indicator, we found experimentally that both the locking bandwidth and the FSBW of the device are inversely proportional to the length mis-match of the two loops. Finally, with dual-loop fiber lengths of 2041m and 2449.2m, including 2039m common fiber loop, we successfully obtained linearly chirped microwave signals around 9GHz with a phase noise of -127dBc/Hz at 10kHz offset from the 9GHz carrier, a FSBW of 0.4GHz, and a chirp rate of 200THz/s at 500.38 kHz repetition rate. More impressively, the side-mode spur ratio of the linear frequency modulated (LFM) signal is reduced to less than -83dB, the lowest ever achieved for a FDML OEO to the best of authors’ knowledge, which is more than 50dB improvement over that achieved with a single loop FDML OEO reported previously.

Optical Tunable Frequency-Doubling OEO Using a Chirped FBG Based on Orthogonally Polarized Double Sideband Modulation

“…To further investigate the relationship between the dispersion of the CFBG and the frequency response of the MPF, we substitute the equation D = −zβ " (ω c )ω c 2 /2πc into Equations (7) and (8). The frequency response of the MPF and the condition of the maximum transmission response can be rewritten as…”

“…Equations ( 7) and (8). The frequency response of the MPF and the condition of the m mum transmission response can be rewritten as…”

“…The first OEO [7] was proposed in 1996, which consists of a pump laser and a feedback loop including an electrical filter, an electrical amplifier, etc. Since the phase noise is directly determined by the loop length fluctuation in general, fiber-based OEOs can use long fiber delay lines to obtain a high Q-factor and ultra-low phase noise microwave signals [8,9]. On the other hand, to realize the large-scale deployment of OEOs, integration technology [10,11] using different photonic integration material platforms can be applied.…”

Implementing competence-based kindergarten teacher education in China : a case study of Hubei University of Arts and Science

“…Optoelectronic oscillator (OEO) exudes an inherent advantage in generating low phase noise signals [11][12][13][14][15] since the first prototype exposed by S. Yao and L. Maleki [16]. Especially, recently novel optoelectronic oscillators are emerged to expand the generated waveform styles and performance for various application scenario [17][18][19][20][21][22][23][24][25][26].…”