A fiber variable ratio coupler, also known as tunable directional coupler (FTDC) has an all-fiber construction and provides the tuning range of 0 – 100 % coupling ratio with negligible optical loss. It is based on evanescent field coupling using two side polished fibers where the coupling ratio is tuned by adjusting the core-to-core geometric offset. Customer specified fibers and operating wavelengths are available including single-mode fibers, polarization maintaining fibers and other specialty fibers.
Working Principle
A fiber variable ratio coupler consists of two side-polished fibers (Please also see the side-polished fiber). Optical fibers embedded in quartz blocks are polished until only a few microns of cladding remain before mating the two blocks with index matching oil in between. 0-100 % coupling ratio can be obtained by adjusting the core-to-core geometric offset. Fiber variable ratio couplers have been used for diverse applications including fiber laser, ring resonator, fiber loop mirror, optical tweezer, interferometer, frequency comb, OFDR, and so on.
Demo Video
• Negligible loss
• Polished fiber coupler
• Tunable coupling ratio (0-100%)
• Available with various fiber types including SMF and PMF
• Available at customer specified wavelength
• Very small size
• Optical system testing
• Interferometry
• General laboratory experiments
• Optics education kits