In the present work, we propose a method to calibrate the instantaneous optical frequency of a tunable laser using frequency comb. The tunable laser is heterodyned with the equally spaced comb lines, and the heterodyne signal then passes through an electronic frequency selection unit. When the optical frequency of the tunable laser is in the vicinity of the comb lines, the output of the frequency selection unit delivers a peak. We analyzed the effect of the characteristics of the narrow bandpass filter (NBF) in the frequency selection unit. Simulated and experimental results show that the characteristic of the output peak is related to the normalized sweeping speed of the input tuning laser source. At small normalized tuning speed, the envelope of the filtered signal follows the amplitude-frequency response characteristic of the NBF. This shows that the filtered signal using Gaussian filter has broader peak than the one using Butterworth filter, due to the slower roll-off behavior in the transition band of Gaussian filters. At large sweeping speed, the envelope of the filtered signal deviates from the amplitude-frequency response character of the NBF. The peak intensity of the filtered signal is attenuated, and the bandwidth of full width at half maximum is broadened. Experiments were carried out to verify the simulated results. In the experiment, the instantaneous frequency of an external cavity laser diode was calibrated using the presented filtering method showing periodic non-linear tuning.
In this study, a numerical model based on finite element method was proposed to evaluate the thermo-mechanical behavior of a composite structure material. The composite structure consisted of substrate, thermal spray coating, and an embedded optical fiber. The stress level of the composite structure especially the embedded fiber at the end of elaboration process was analyzed. The variations of refractive index of the embedded fiber due to the thermo-optic effect and the elasto-optic effect were investigated. The results showed that the the variation of stress and refractive index during the elaboration process had an insignificant effect on the embedding quality of the optical fiber under the presented optimized experimental conditions.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.