Research On The Environmental Adaptability And Accuracy Of Optical Fiber Delay Line

Using optical true-time delay(OTTD) phase shift technologies based on optical fiber delay lines(OFDL) to replace the traditional electric phase shift technologies can overcome the beam deflections, solve the signal broadening problems and extremely elevate the instantaneous bandwidth in phased array antenna systems. When concerning about its applications, the adaptive capacity to environment of optical fiber delay lines would directly affects the properties of instruments. Thus, it is essential to increase the accuracy, the environmental suitability and the reliability of optical fiber delay lines.Firstly, an experimental platform is set up based on the vector network analyzer phase measurement whose single-point fiber delay precision is ±0.1ps. After analyzing the state delay deviation of magnetic-optical switch, the topology of optical fiber delay line was designed and optimized, and a high-precision 5-bit optical fiber delay line with a delay stepping of 10 ps is developed whose delay accuracy, standard deviation of delay error, and average loss is ±1.1ps, 0.68 ps and 5.42 dB respectively. In addition, the standard deviation of amplitude error is less than 0.49 dB.Then, the temperature characteristic of optical fiber delay line and classic optical configurations of magneto-optic switch(MOS) is analyzed. Three major causes that the temperature induced additional losses of MOS are pointed: the temperature-introduced45°optical rotatory angle deviation of optical plate, the temperature-introduced magnetic-optical crystal rotatory angle deviation and the spatial mismatch of temperature-introduced fiber coupling. By combining the temperature characteristic of crystal and the coupling efficiency of fiber’s mode field, the additional losses of MOS resulting from the three causes above are calculated. The analysis showed that the temperature have little influence on the 5-bit OFDL.After that, the radiation effects of optical material, the generation of color-center and the performance of the radiated OFDL is analyzed in the radiation environments. By introducing the dynamic model of silicon material E’ color-center in low-energy particle irradiation and the radiation characteristic of optical fiber on the base of the previous study, the radiation characteristic of 5-bit OFDL is analyzed and the idea of anti-radiation technology is presented.Finally, a temperature test system and a radiation test system are set up, including5-bit OFDL, optical fiber, MOS, optical fiber splitter(OFS) and wavelength division multiplexer(WDM) under test. When the temperature is set from-5℃ to 55℃, the results below: the temperature-induced additional loss(TIAL) of the two MOSs is around 0.16 dB and 0.41 dB respectively; the TIAL of the OFSs and the WDM are all less than 0.1dB; the delay deviation of the 5-bit OFDL is 2.2ps, standard deviation of delay error is 0.4~0.5ps, the range of loss is 5~6dB, the standard deviation of amplitude error is less than 1dB and the TIAL is less than 0.5dB. Test results show that the temperature have little influence of a 5-bit OFDL of a small step. When the irradiation dose is set from 0krad to 120 krad, the results below: the irradiation-induced additional loss(IIAL) of the 5-bit OFDL and other devices is increasing with the increase of irradiation dose, the IIAL of MOS and OFS are all around 1dB and he IIAL of WDM is around 4dB, but the IIAL of 5-bit FDL even reach to 19 dB, moreover, the 1.55 mm aluminum shell cannot effectively lessen the damage caused by irradiation.