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We present a Frequency-domain optical coherence tomography (FD-OCT) system for intravascular imaging. The whole system consists of 4 parts: imaging catheter (IC), motion controller (MC), optical engine (OE) and data acquisition and processing module (DAPM). By using swept laser source with 50 KHz sweep speed and high speed optical rotary jiont, we can get 100 frames per second (fps) and scan 20 mm vessel per second.

With the superiority of anti-electromagnetic interference, corrosion resistance, light quality, small size and so on, optical fiber sensing technology is widely used in aerospace industry, petrochemical engineering, power electronics, civil engineering and biological medicine. It can be divided as discrete and distributed. Discrete optical fiber sensing utilizes fiber sensitive element as sensors to detect the quantity to be measured. Optical spectrum, light intensity and polarization are usually used as the sensitivity parameter because they can be modulated by parameter such as rotation, acceleration, electromagnetic field, temperature, pressure, stress, stress, vibration, humidity, viscosity, refractive index and so on. Fiber works as the channel and links the fiber sensor and demodulating equipment. After a long period of research, the discrete optical fiber sensing technology stretch out many branches, we discussed the most representative ones as follows, the fiber grating sensing technique, the fiber fabry perot sensing technique, the fiber gyroscope sensing technique, the fiber intracavity sensing technique, the fiber surface plasma sensing technique, hollow-core fiber whispering gallery mode sensing technique, magnetic fluid fiber sensing technique and fiber-based optical coherence tomography sensing technique. Based on optical effect as rayleigh scattering, Raman scattering and Brillouin scattering, distributed fiber sensing system uses fiber itself as a sensor, when the vibration, stress, voice or temperature acts on the fiber changes, the optical signal transfers inside the fiber will change accordingly. The fiber distributes in a large range and a long distance, then the signal can be located at different positions and realize the multi-position measurement. We discussed the main distributed fiber sensing technologies as follows, the interferometric disturbance fiber sensing technology, the optical frequency domain reflectometry fiber sensing technology, the -optical time domain reflectometer fiber sensing technology, the optical fiber Brillouin sensing technology and the optical fiber Raman sensing technology. The development of technology is promoting the integration and network of optical fiber sensing, now it also becomes a research hotspot. Fiber optic smart sensor network is formed by various discrete and discrete optical fiber sensors in certain topological structure with the function of self-diagnosis and self-healing. Current research concentrates in the following areas, the increase of the multiplex sensor number, the topological structure with higher robustness and the intelligent control of sensing network. In this paper, we discuss the origination, development and research progress of discrete, distributed optical fiber sensing technologies and optical fiber sensing network technology, and the future research direction is also prospected.

To improve the reliability that are very important for large-scale and long range all optical fiber sensor networks, monitoring optical fiber sensor networks is necessary. We proposed a novel method for monitoring optical fiber sensor networks using optical frequency-domain reflectometry (OFDR) which provides a narrow spatial resolution that enables us to locate closely separated reflection and discrete sensors such as fiber sensing grating and other microstructure fiber sensors. Moreover, thanks to the inherently coherent detection, a high dynamic range can be realized that allows the measurement of Rayleigh backscattering throughout a fiber network. Namely, OFDR also can monitor distributed fiber sensors By using narrow linewidth laser, OFDR's monitoring range satisfies the requirements for long range optical fiber sensor networks. In our OFDR system proposed, we can achieve to monitor optical fiber sensor networks with measurement range of a few tens of kilometers in a sub-cm spatial resolution.