SMS struktura in rodovno sklapljanje
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UMUM
Fiber-optic microbend sensor structure

We proposed and experimentally investigated a novel microbend sensor structure. The structure is composed of single-mode leads and multimode sensing fiber. The proposed structure exhibited a level of sensitivity as much as six times higher than that of the classical microbend sensor configuration when the same sensing fiber was used. Additionally, single-mode leads reduce lead noise and allow the use of more-coherent sources. The total loss of the proposed nondeformed structure is near 2 dB when the proper splicing method is used.

Propagation of the fundamental mode in curved graded index multimode fiber and its application in sensor systems

A novel principle of light transmission through very small radius bend in optical fibers is presented. The potential applications of the proposed structure are fiber optic sensors and other fiber optic systems. The design makes use of graded index multimode fiber as transmission medium. However, the feed to the multimode fiber is through a single mode fiber to ensure that only the lowest order spatial mode is launched. Similarly the receiver is also coupled to the sensing element through a single mode fiber. The fundamental mode within graded index multimode fiber proves to be very insensitive to macrobends if bend radius is larger than certain critical value. If bend radius is reduced below critical value the loss increases very rapidly and this allows for construction of relatively sensitive macrobend fiber optic sensor. This work presents a quantitative theoretical model of the proposed structure and a detailed experimental investigation of structure with possibilities for its practical applications.

Microbend sensor structure for use in distributed and quasi-distributed sensor systems based on selective launching and filtering of the modes in graded index multimode fiber

This paper describes a novel optical fiber microbend sensor architecture which my be utilized in distributed and quasi-distributed measurement. The actual sensor element is graded index multimode fiber coupled to the measurand field through the usual microbend inducing structures. However, the feed to the sensing section is through a single-mode fiber spliced to the multimode fiber to ensure that only the lowest order spatial mode is launched. Similarly the receiver is also coupled to the sensing element through a single mode fiber. The single mode within multimode fiber propagates with minimal mode coupling with source to receiver losses of typically 0.7 dB for short sensors ranging to approximately 0.3 dB per each additional kilometer of sensing fiber. The sensitivity of this structure to microbend induced losses has been thoroughly characterized. Typically the optical power loss for a given microbend structure and force is about three to six times higher in this architecture than for conventional fully mode filled microbend sensor. The structure is also almost totally insensitive to macrobend induced losses and allows a variety of novel designs in microbend inducing structures. Additionally, spatial mode filters allow effective control over concatenation effects that are common in microbend sensors

Low-loss transmission through tightly bent standard telecommunication fibers

This letter presents a principle of low-loss light transmission through tightly bent standard telecommunication optical fibers. The design is based on selective launching and filtering of the fundamental mode in standard graded index multimode fiber. The proposed system has demonstrated significantly better macrobend tolerance than commercially available bend resistant fibers. 2000 American Institute of Physics.