Font Size: a A A

Research On The Tuning Technology Of FBG Based On Two-fixed-end Elastic Compressive Bar

Posted on:2011-01-30Degree:MasterType:Thesis
Country:ChinaCandidate:D Z YangFull Text:PDF
GTID:2178360305951779Subject:Electromagnetic field and microwave technology
Abstract/Summary:PDF Full Text Request
Since the first fiber Bragg grating (FBG) was written into a Ge-doped fiber by the method of standing-wave in 1978, FBG have become a notable photonic device in all-optical network and fiber sensor network, for its abundant frequency selection characteristic, low insertion loss, excellent tuning performances and naturally compatibility with fiber.The method of tuning FBG based on the two-fixed-end compressive bar have been investigated deeply both in theory and experiment. The main content of this thesis include following aspects:1. The development history of FBG, the basic conception of FBG and the sorts of FBG are briefly reviewed, the techniques of writing FBG are also summarized.2. Common analysis theories of FBG are introduced. Based on index modulation model, the coupled mode equations are derived by eigenmode expansion of light field. By the given boundary conditions, the reflectivity formula of uniform FBG is obtained. The influences of grating length and index modulation depth on uniform Bragg grating are analyzed. Reflection characteristics of chirped fiber Bragg grating are described by transfer matrix method which divides the grating into many uniform gratings. The influences of grating length, chirp parameter and index modulation depth on chirped fiber grating are demonstrated in detail.3. A system of tuning the FBG based on the step motor is design. The system includes the upper computer software, the MCU circuit, the driver and the step motor. The upper computer software is designed using the C++Builder, the function including the running direction, distance, speed and the subdivision control by serial port. The MCU circuit is designed using Prote199Se and Keil C language。4. A novel tunable wavelength filter is designed and demonstrated, which is realized by bending a fiber Bragg grating mounted on a two-fixed-end elastic compressive bar. According to material mechanics, equations are derived relating the wavelength tuning of fiber Bragg gratings to the bending strain. The fiber grating wavelength tuning experiment are carried out using self-designed tuning apparatus. The resonant peaks phenomenon during tuning process is analyzed in detail. The wavelength change has a strictly exponential curve relationship with the displacement of the translation stage. The experimental tuning range is larger than 35 nm and the 3dB bandwidth change is less than 0.09 nm. The tuning has nice repeatability with the hysteresis of 0.08%.A novel method for tuning the chirp ratio of fiber grating without the central wavelength shift is proposed using a two-fixed-end compressive bar which induces a linear strain distribution along the grating. The chirp ratio tuning principle is analyzed according to material mechanics and the reflection and time delay characteristics of the grating during the tuning process are simulated as well. The bandwidth tuning range is from 6.52 nm to 12.78 nm when the grating is tuned in the broadening way, meanwhile, the bandwidth tuning range is from 6.57 nm to 0.95 nm in the compressing way.5. The application of chirped fiber grating for dispersion compensation in optical fiber communication and the application of true time delay of the chirped fiber grating for phase array radar are briefly introduced.
Keywords/Search Tags:chirped fiber Bragg grating, wavelength tuning, chirp ratio tuning, dispersion compensation, true time delay
PDF Full Text Request
Related items