Characteristics Analysis Of The Diffraction Far-field Of The Optical Waveguide And The Measurement Device

With the development of optical communication technology, people put forward the increasing demands on the information transmission speed and the capacity. And the requirement of high-performance, highly integrated optical devices is increasingly urgent. The transmission characteristics of optical waveguide mode field considered as the theoretical basis of the production of optical devices is important. Spatial frequency spectrum is the physical quantity that is used to describe the output characteristics of optical waveguide end surface. In this paper, the feature of the diffraction far-field distribution from the end surface of TE1mode in planar optical waveguide is analyzed. By the method of mathematical modeling, a fitted function reflecting the relationship between the diffraction spectrum and structure parameters has been found.In this paper, a new detection device, which can automatically detect the diffraction far-field intensity distribution from the end surface of the optical waveguide, is discussed. The working principle of diffraction intensity distribution detection device is introduced. Under the action of the driving voltage, the linear deflection of galvanometer following by the diffraction intensity from the end surface of the optical waveguide is reflected into a photoelectric detector, so that the optical signals are converted to electrical signals. At the equal time interval, the electrical signals will be sampled by a single-chip microcomputer, so that the intensity of the same diffraction angle will be sampled in each cycle. Then the same diffraction point will be multiple sampled, and the light intensity value of the diffraction angle can be detected by the lock-in amplifier. Then a phase-shift sampling pulse sequence is generated by the single-chip microcomputer, so that the next signal point is sampled. With this method, the light intensity value of each diffraction angle from the end surface of the optical waveguide can be detected. By using the measuring device to detect the light intensity distribution from the end surface of the fiber, the purpose that the light intensity distribution of the optical waveguide can be automatically detected when the photoelectric detector is in immobile circumstance, can be realized. In order to achieve the purpose of measuring the detected electrical signals, in this paper, a detection circuit and control sampling circuit are designed. And the actual measurement of the intensity distribution from single mode fiber end surface, the measurement result verifies the feasibility of the measuring device.