A side-polished fiber, also known as half coupler provides access to the evanescent field of light guided in an optical fiber with negligible insertion loss. Various materials can be used to induce interactions with the evanescent field to create desired optical functions. Customer specified polishing depth is available for single-mode fibers, polarization maintaining fibers and other specialty fibers.
Working Principle
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The side-polished fiber comes in a quartz substrate with a flat surface to provide easy access to the evanesent field for various solid or liquid materials. An optical fiber is embedded in the engraved V-groove in a quartz block and polished until the remaining cladding is a few microns thick. The distance between the removed cladding to the top part of the fiber core can be estimated by measuring the optical transmission through the fiber when index matching oil is placed on the polished surface (oil drop test). As shown in Fig. (c), the transmission rapidly decreases when the effective index of the guided mode coincides with that of the index oil. The maximum loss depends on the thickness of the cladding from the core.
Various type of side-polished fibers
Standard circular core optical fibers, polarization maintaining fibers and few-mode fibers can be polished with target polishing depth. For the PM fiber, customers can specify any orientation of the PMF axis. The standard size of the quartz substrate is 5(H)X10(W)X27(L) mm and customized size is also available, as small as 2(H)X2(W)X22(L) mm.
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• Negligible loss
• Various substrate (quartz) dimension
• Available with various fiber types including SMF, FMF, and PMF
• Available at customer specified polishing depth
• Optical communication
• Fiber optic sensors
• Fiber laser