Low-loss laser-to-fiber coupling with negligible optical feedback

Simulation of 4 × 4 light coupling to a single-mode fiber

“…The numerical aperture of our proposed microlens is 0.1 for the entire array. We also have proposed some solutions for increasing the optical-power-coupling efficiency with a variety of millimeter and sub-m optical devices via microlens arrays [13,14]. These microlens arrays are useful for meeting the requirements of the miniaturized and monolithic VCSEL.…”

A development of a novel TEC-lensed fiber with working distance of 60μm using a standard single-mode fiber

“…Lensed fibers have been proposed to improve the coupling efficiency and are suitable for optical couplings in applications to such as compactness, simplicity, stability, and freedom from bulky lenses [1]- [4]. Conventional lensed fibers using a SMF have a short working distance (generally shorter than 10㎛), tight displacement tolerance (~0.3㎛ for 1-dB loss) in simple butt coupling, and critical fabrication process (lens radius ~5㎛) [1]- [3].…”

Optical coupling method utilizing a lensed fiber integrated with a long-period fiber grating

“…A working distance longer than ϳ100 m is generally desired for LD-to-SMF packaging of an optical subassembly module 10 and for the reduction of op-tical backreflection. For example, in the case of lensed fiber with a 50-m radius, the optical backreflection decreases from Ϫ30 to Ϫ60 dB when the working distance increases from 10 to 100 m. 11 Although it has been reported that an integrated spot size converter improves coupling, 12 the working distance is typically not more than 20 m; thus higher optical backreflections can be induced for an uncoated and cleaved fiber. Various approaches to increasing the working distance have been tried, but most working distances are still limited to less than 50 m. 13,14 Although the use of thermally expanded core fiber integrated with a coreless fiber could lead to a larger working distance, the fabrication processes with this type of fiber are relatively time consuming and complicated.…”