Study Of Semiconductor Laser Control Technology Based On Field-programmable Gate Array

With the continuous advancement of the optical fiber technology,optical fiber sensing field is also growing rapidly.Fiber optic sensors acquire information through optical fibers.They have advantages such as small size,high sensitivity,large dynamic range,wide measurement range,strong reusability,strong anti-interference and strong adaptability to the environment,so that they are widely used in various fields.Wavelength tunable semiconductor lasers can play an important role in white optical fiber sensing measurement systems,so that people are always focus on how to optimize their performance.FPGA is a kind of programmable logic devices,which has the advantages of rich resources,fast operation and high flexibility.Applying it to the white optical fiber sensing measurement system can not only help improving the wavelength tuning speed of the wavelength scanning laser source,but also meet the optical fiber sensing demodulation system's demand for real-time processing of a large number of data.What's more,it can help promote the integration and flexibility of the white optical fiber sensing measurement system.In this paper,we compare several kinds of wavelength tunable semiconductor lasers and finally choose SGDBR laser as the wavelength scanning laser source of this white optical fiber sensing measurement system.After analyzing the working principle and control mode of the SGDBR laser in detail,we choose 5 serial or parallel channels of ADN8810 digital constant current source to input the 5 control current required by the laser.And also we choose FPGA as the core control element of the whole wavelength scanning laser source.We mainly carries out the logic coding work of FPGA,driving the whole hardware link to realize single-wavelength laser output and wavelength cycle scan output.The light source system has5014 output laser wavelength points,a wavelength range of about 1527 nm to 1567 nm and a wavelength interval of about 8pm.For the data acquisition system,we choose TLV5618 to analog signal source,AD9226 to converse the analog signal into digital signal and choose FPGA as core component for data acquisition and transmission.We realize DA chip driven,AD conversion data acquisition and storage control through coding FPGA.And through the hard and soft core,we complete the design of data storage module and UART serial/standard Ethernet port transmission module,and finally realizes the complete SOPC system.The tests show that the data acquisitionsystem can normally collect and store data,and FPGA can control to upload the collected signal strength data to PC through UART serial port or standard Ethernet port for subsequent processing.What's more,a complete white optical fiber sensing measurement system is built by combining the designed wavelength scanning light source system and data acquisition system.In this paper,we make three F-P fiber optic sensors with different cavity length values and do the acquisition of interference spectrum and the demodulation of sensor cavity length by using both self-made white optical fiber sensing measurement system and SM125 commercial optical fiber sensor demodulator.By comparing the test results,it is found that the interference spectra collected by the two systems are approximately coincident,and the demodulated sensor cavity length values are within 10 nm,which verifies the feasibility of the self-made white optical fiber sensing measurement system.The white optical fiber sensing measurement system finally realized in this paper has the advantages of small size,high value performance and upgradeability.It can be used for white optical fiber sensing measurement or as a separate cyclic scanning light source.