Modulation And Transmission Characteristics Of A Monolithic Injection-locked DFB Laser

With the rapid development of optical communication technology,people are increasingly pursuing the speed and capacity of information transmission.This also puts forward higher request to semiconductor photoelectron technology.As a light source of optical communication,semiconductor laser is also an indispensable link in the development and progress of optical communication.So it is of great significance to develop a laser with good performance.In order to improve the performance of semiconductor lasers,various kinds of semiconductor lasers with different special structures have been developed.This paper mainly introduces a monolithic optical injection-locked(MOIL)DFB semiconductor laser.The frequency chirp and SSB modulation characteristics are studied,as well as the transmission characteristics of the laser.The specific work is as follows:The design and epitaxial structure of a monolithic optical injection-locked DFB laser based on REC technology are studied.The static performance of the laser is tested.Including the detuning frequency and the power injection ratio.A heterodyne beat frequency method was proposed to verify the suppression of the frequency chirp of the MOIL laser.Comparing to the free running of the slave laser,the frequency chirp of the laser in the injection locked state decreases from 11.42GHz to 0,84GHz.The frequency chirp of the MOIL laser is evaluated based on the spectral characteristics.The results show that comparing to the value in the free running state,the half-height and width of the laser in the injection lock state decreased from 0.1067nm to 0.0123nm.The corresponding frequency chirp decreases from 13.3GHz to 1.4GHz.When in the injection-locked state,the frequency chirp of the laser is suppressed.The principle of realizing SSB modulation by optical injection locking is analyzed.The single-side band modulation of MOIL laser is realized experimentally.In the injection locked state,the maximum Pusb/Plsb value increases from 1.862dB to 29.2dB when the slave laser operates freely.The Pusb/Pisb value also increases when the modulation signal power increases.The experiment proves that after 50km optical fiber transmission,the normalized optical fiber transmission response of the MOIL laser in the injection locked state was significantly lower than that in the non-injection locked state,because the optical fiber dispersion in the transmission system was suppressed.At the same time,the electric power is tested under the injection locking state.The results show that the electric power varies linearly with the length of the fiber,and the transmission is not affected by the dispersion of the fiber.Finally,the EVM and BER values of MOIL laser are tested and calculated.In the specific injection locking state,Error Vector Magnitude(EVM)is kept below 5%after 25km and 50km optical fiber transmission and the maximum bit error rate(BER)is 10-10.These results prove that when the MOIL laser is under the specific injection locked state,the dispersion in the fiber transmission system is suppressed and the performance of the transmission system is greatly improved.