Research On Microwave Photonic Filter Based On Broadband Optical Source

With the rapid development of information technology,low-band,low-rate microwave frequency band resources have been difficult to meet the needs of people's current material culture,and people's demand for high-speed and large-capacity wireless data transmission is getting higher and higher.In the context of this demand,the study of the interdisciplinary interaction between optics and microwave,microwave photonics,has attracted a lot of attention from academics,industry and industry.The generation,transmission and processing of high frequency microwave signals based on traditional electric domains will face problems such as electronic bottlenecks.However,photonics has the advantages of large bandwidth,low transmission loss,immune to electromagnetic,etc.,and generates,transmits and processes high-frequency microwave signals through microwave photonics.There is no doubt that microwave photonics is an ideal for high-frequency microwave signal processing.In this paper,we will mainly study the microwave signal processing.Comparing the microwave photonic filter with the traditional electrical domain filter,we can get the disadvantage of the electrical domain filter in addition to the serious transmission loss.Another disadvantage is that the passband center of the required filter.When the frequency changes,the circuit must be redesigned to meet the frequency change requirements.Microwave photonic filter is an important direction in microwave photonics research.It can directly process RF signals in the optical domain,which increases the complexity of the device to a certain extent,but gives the microwave photonic filter a lot of advantages,including large bandwidth.,low loss,light weight,immune to electromagnetictunable and reconfigurable.In this paper,the concept of the microwave photonic filter is introduced by introducing microwave photonics.The research status of the microwave photonic filter at home and abroad is reviewed.The key components needed in microwave photonic filter are introduced briefly.The basic principle and related performance parameters of the filter are explained in detail.The single-passband microwave photonic filter of traditional spectrum-sliced and equivalent-electrical-slicing for the broadband light source is studied.By slicing the broad spectrum source instead of the expensive laser array,the cost and complexity of the system are reduced.The operation principles of the two schemes are theoretically analyzed and deduced.The limitations of the traditional spectrum-slicing-based microwave photonic filter are analyzed and the superiority of equivalent electrical-slicing is derived.The schemes were verified by experimental results and Matlab simulation.A microwave photonic filter based on reflective fiber Mach-Zehnder interferometer is proposed,which is theoretically verified and experimentally verified.The broadband optical source is sliced by a reflective fiber Mach-Zehnder interferometer to act as a multi-wavelength light source,and a single-mode optical fiber is used as a delay unit to implement a microwave photonic filter.the conversion between the left passand band and the right passband can be realized by adjusting the polarization controller,and the double passbands can also be realized.The filter center frequency can be tuned by adjusting the optical variable delay line.By cascading a fiber ring,the Q value of the filter is increased.The experimental results show that the 3dB bandwidth of the dual-passband is 210 MHz,which is 150 MHz higher than that of the non-cascading fiber ring.When two erbium-doped optical fiber amplifiers are used,the suppression ratio is increased to 30 dB.