CO 2 -laser-beam-based technique for producing optical fiber components

Abstract

A simple and handy technique to produce optical fiber components such as Bragg gratings has been used. A C02 laser beam, focused on a single mode fiber, can change its optical properties locally, allowing therefore the creation of a Bragg grating inside the fiber it-self. In the present study, we investigate the effect of this laser beam on the fiber and show how optical fiber components can be produced. When exposing a single-mode optical fiber to a high-power C02 laser beam a small device is developed inside this fiber. Inside this micro-structure, the optical power is exchanged between the core and the cladding modes. This device may exhibit either a very selective rejection behavior similar to Bragg grating or an oscillating behavior like tapered fiber. The coupled mode theory combined with a mathematical algorithm can be used to study the propagation of the modes involved in the fiber.

Using an electrical arc for fiber components implementation

“…The optical fiber with is considered as an ideal fiber with refractive index variations and core radius perturbations. Mathematically, we can find the eigenvalues by solving the continuity equations of the longitudinal field components and theirs derivatives [15]. When considering a finite cladding, these equations are given by (Eq.…”

“…The coupling coefficient C jk between jth and the kth mode is given in reference [15]. In order to solve the coupled mode equations, we have calculated a new expression of coupling coefficients (equation 3).…”

“…After several arc, separated by precise distance, we can notice an attenuation of the light spectrum used for the experience. For micro-deformations we can use also a CO2 laser beam [15]. If the fiber core radius after deformation become smaller than the cutoff frequency radius, the core mode becomes a cladding one.…”

“…But ultimately the UV grating inscription requires expensive and complex laser equipment. Recently several photo-insensitive fabrication methods have been reported [13,14,15,16,17,18,19,20] which eliminate some of the problems mentioned above. In the present paper we will primarily focus on the electric-arcbased fabrication technique.…”

“…Micro-deformations allow the modulation of the effective index of fiber propagated modes and allow LPFG writing on a single mode fiber. By using the theoretical analysis presented in reference [15], we can treat the wave propagation inside the LPFG that exhibits fundamental mode coupling with the cladding modes. In this analysis, the use of a fiber optic welder for the fabrication of LPFG will be demonstrated based on actual experimental results.…”