The measurement of distance plays an important role in many aspects of modern societies. In this paper, an absolute distance measurement method for arbitrary distance is proposed and demonstrated using mode-resolved spectral interferometry with a gain-switched dual comb. An accuracy of 12 µm, when compared to a He-Ne fringe counting laser interferometer, for a displacement up to 2.5 m is demonstrated by tuning the repetition frequency of the dual comb from 1.1 GHz to 1.4 GHz. The compact measurement system based on a gain-switched dual comb breaks the constraint of periodic ambiguity. The simplification and improvements are significant for further industrial applications.

A highly miniaturized, single-chip, large scanning range MOEMS scanner is demonstrated. This intrinsically-aligned, monolithically integrated device uses small angular displacement to provide a linear scanning range of 2000 μm in the lateral and 1000 μm in the vertical direction, at a working distance of 2 cm, with an average operating power lower than 170 mW. Within a footprint of only 7×10 mm 2 , the presented system fully integrates a photonic interferometer comprising a mirror, a silicon microlens and the MEMS actuator into a single chip, thus offering an unprecedentedly miniaturized scanning solution. The monolithic integration of all photonic components provides intrinsic alignment and excludes coupling losses often encountered in systems composed of discrete parts. No additional attenuation of the optical signal is observed during device operation. This small and highperformance device is suitable as complete system-onchip for commercial, portable imaging applications.

The measurement of distance plays an integral part in many aspects of modern societies. In this paper an integrated mode-locked laser on a chip is used for distance measurement based on mode-resolved interferometry. The emission from the on-chip source with a repetition rate of 2.5 GHz and a spectral bandwidth of 3 nm is coupled into a Michelson interferometer. The interferometer output is recorded as a spectral interferogram, which is captured in a single camera image. The images are analyzed using Hilbert transform to extract the distance. The distance derived shows a deviation of 6 μm from the reference, for a distance up to 25 mm. We also demonstrate interferometry with repetition frequency sweep which can also be used with the source. Performance is expected to be better in the near future with the rapid developments in the field of on-chip laser sources which are demonstrating larger spectral widths and coherence lengths.

The main principle of the existing optical gyroscope is based on the Sagnac effect. How to improve the measurement accuracy of the Sagnac effect is an important research topic of improving the gyro accuracy. The traditional optical gyro uses the short wavelength characteristic of light to improve the detection accuracy. But when considering the fact that the detection accuracy of the microwave phase/frequency is much higher than that of light wave phase/frequency, if the microwave can be used to detect the Sagnac effect, the detection accuracy higher than optical gyro accuracy can be obtained, which makes it possible to achieve high-accuracy microwave gyro. The Sagnac effect is detected by using the optoelectronic oscillator based light-carrying microwave structure. Experimental results prove the feasibility of detecting Sagnac effect by using microwave, which lays the foundation for realizing the high-precision microwave resonant gyroscope in the future.

Traditional laser range technology has a poor phase measurement accuracy and an additional phase of the system, which restricts the improvement of its accuracy. In this article, by using the technology of variable frequency measurement based on double polarization modulation the phase shift range-finding technology is improved. With the method of double polarization modulation, the demodulation of the phase information is directly implemented on the phase modulator, which can make the system simpler. The variable frequency technology is used to replace the traditional phase discrimination technology; therefore the measurement accuracy of the system will not be persecuted with the phase crimination any more. The theoretical curve of sine (cosine) relation between modulation frequency and output light intensity is proved experimentally. Owing to the fact that the stability of frequency can be better than 10-6, the measurement accuracy can reach ±10.6 u m@4.5 m. By using this system to measuring a 200 m-long fiber, the clear curve of modulation frequency versus output of system is obtained.