In this paper, the uncertainty on the phase noise measured for a low phase noise compact optical delay line optoelectronic oscillator is evaluated as ±2 dB at 2 σ.
Optical resonators are useful to achieve optoelectronics oscillators or frequency combs. High-Q factor resonators for photonics applications are obtained by polishing. To gain in terms of performance, a way is to perform a controlled annealing process to improve the roughness of resonator’s surface down to the nanometer scale. We present the setup and explain it.
To obtain high quality factor optical resonator, we must reduces stresses at the periphery of their surface as mechanical treatments enable state-of-the art characteristics for the surface roughness. This process is driven by electronics significantly improved thanks to electronic boards based on the use of intensity pulses, coupled with feedback on several parameters for fitting the specific profile of the heating cycle. Sensor is based on K-type technology to reach specification up to 1000°C. Technology is based on the use of microcontroller, low noise operational amplifiers, field effect transistors and diode bridges and driven by a intensity signal.
Thermal annealing performed during process improves the quality of the roughness of optical resonators reducing stresses at the periphery of their surface thus allowing higher Q-factors. After a preliminary realization, the design of the oven and the electronic method were significantly improved thanks to nichrome resistant alloy wires and chopped basalt fibers for thermal isolation during the annealing process. Q-factors can then be improved.
In this paper we report the realization of a specific electronics and oven for optical resonator which needs to be
temperature controlled during its annealing process to increase its quality factor for optoelectronic oscillator application.
In order to stabilize the signal delivered by an optoelectronic oscillator (OEO) [1-5], it is necessary to lock the signal of the laser on the resonance. The laser wavelength must be stabilized onto one of the resonator’s resonances to be able to maintain a stable performance of the oscillator. We first present the Pound Drever hall method that has been used to realize this setup. As an alternative method, we have also investigate another technique based on the use of acousto-optic cells (AOC). It is presented on part 3 of this paper.
The use of a shorter delay line in a optoelectronic phase noise measurement system working in X-band, allow a
characterization of the phase noise far from the carrier. Fourier frequency analysis can be extended from 105 to 2.106 Hz
by introducing a 100 m delay line in addition of a 2 km optical fiber.
The performance advances in communication systems like Radar system, precision navigation, space application and
time and frequency metrology require more stable frequency and low phase noise system. Here is presented a
configuration of phase noise measurement system operating in X- band using a photonic delay line as a frequency
discriminator. This system doesn't need any excellent frequency reference and works for any frequency between 8.2 and
12.4 GHz. Using cross correlation on 500 averages, noise floor of the instrument is respectively -150 and -170 dBc/Hz at
101 and 104 Hz from the 10 GHz carrier (-90 and -170 dBc/Hz including 2 km delay lines). This instrument is developed
in the context of association with the national french metrology institute (laboratoire national de métrologie et d'essais,
LNE). This calibration system is to be integrated in measurements means of the accredited laboratory to improve the
Calibration Metrology Capabilities (CMC) of the LNE.
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