OCT resolution enhancement using long-period fiber grating and erbium-doped fiber

We proposed a technique to improve OCT resolution using LPG and EDF. The proposed technique improves the resolution of OCT by reshaping the spectrum of ASE source into Gaussian-like form. The ASE source has a strong characteristic peak due to erbium that is used for doping material in EDF. To reduce the peak-induced artifact to OCT image that may degrade image quality and distort inner structure information, LPG is used as a strong ASE peak rejection filter and EDF does a function of absorber when pumping power is not applied. Both of them can do spectral tailoring function properly so that modified source shape and sidelobe suppression can be performed. With the LPG-assisted reshaping, we have enhanced the spatial resolution up to 5 times (similar to200 mum resolution was reduced to about 40 mum). With EDF absorber, we can obtain reshaped ASE source hence resolution was enhanced from 25 mum to less than 20 mum). The spatial resolution can be further enhanced by using cascaded LPGs or control of EDF parameters such as doping material, doping concentration, and the length of used EDF.