Abstract
The objective of this paper is to demonstrate the interest of a consolidation process associated with the powder-in-tube technique in order to fabricate a long length of specialty optical fibers. This so-called Modified Powder-in-Tube (MPIT) process is very flexible and paves the way to multimaterial optical fiber fabrications with different core and cladding glassy materials. Another feature of this technique lies in the sintering of the preform under reducing or oxidizing atmosphere. The fabrication of such optical fibers implies different constraints that we have to deal with, namely chemical species diffusion or mechanical stress due to the mismatches between thermal expansion coefficients and working temperatures of the fiber materials. This paper focuses on preliminary results obtained with a lanthano-aluminosilicate glass used as the core material for the fabrication of all-glass fibers or specialty Photonic Crystal Fibers (PCFs). To complete the panel of original microstructures now available by the MPIT technique, we also present several optical fibers in which metallic particles or microwires are included into a silica-based matrix.
Highlights
Standard silica singlemode optical fibers are widely used in many applications, such as optical components, fiber sensors, non-linear optical devices, and for long-haul telecommunications.In the 1970s, research efforts were mainly focused on the development of efficient processes for elaborating highly transparent materials and for fabricating optical fibers with attenuation coefficient as low as possible in the telecom wavelength bands.Chemical Vapor Deposition (CVD) techniques and synthesized-silica glass became the main actors of optical fiber success, with an attenuation coefficient record as low as 0.15 dB/km at the 1550 nm wavelength (PureBand® Sumitomo, Japan)
To demonstrate the potentiality of the Modified Powder-in-Tube (MPIT) technique for fabricating new specialty fibers composed of metals and glasses, we have investigated and tested the realization of three classes of fibers composed of (i) a silica core including copper particles; (ii) a copper wire surrounded by a silica cladding; (iii) a Photonic Crystal Fibers (PCFs) with copper wires into the air/silica microstructure
We have presented in this paper an original route to produce specialty optical fibers, based on the powder-in-tube technique combined with a consolidation process realized under specific oxidizing or reducing atmosphere
Summary
Standard silica singlemode optical fibers are widely used in many applications, such as optical components, fiber sensors, non-linear optical devices, and for long-haul telecommunications. Ballato and colleagues (at Clemson University, United States) have reused the rod-in-tube technique for fabricating specialty optical fibers from a rod of a specific material (such as Silicon) filled in a silica tube [7] They have used the powder-in-tube method that consists in filling a tube with a powder material and drawing directly this preform down to an optical fiber [8]. Silitec Fibers SA proposed and patented [10] an extension of this concept for producing single-mode optical fibers by replacing the thick and expensive overcladding silica tube of the fiber preform (fabricated by MCVD) with synthetic pure silica powder, leading to a large reduction of the fabrication costs This industrial development was achieved by adding an intermediate process stage that consists in consolidating the preform filled with powder, for enabling stable and long fiber length productions with high reproducibility. Examples of specialty optical fibers fabricated with MPIT technique are presented in Section 3 in order to demonstrate its potentialities for developing optical fibers composed of different glasses or of silica and metal
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