Long period fibre gratings photoinscribed in a microstructured polymer optical fibre by UV radiation

Abstract

Long period gratings were written step-by-step in microstructured poly(methyl methacrylate) (PMMA) fibre using a continuous wave HeCd laser at 325nm irradiating the fibre with a power of 1mW. The grating had a length of 2 cm and a period of 1mm. A series of cladding mode coupling resonances were observed throughout the spectral region studied of 600 to 1100nm. The resonance wavelengths were shown to be sensitive to both surrounding refractive index and the water content of the polymer fibre.

Fabrication of Polymer Optical Fibre (POF) Gratings

“…However, most of the researchers used the optical method to inscribe POF gratings. The optical method can further be classified into four kinds: Interferometeric method [56,69,74,77,78,79,80],Phase mask method [29,64,68,85,95,100,143],Amplitude mask method [67,71,72,73,75,135,136],Direct writing method [66,76,99,109,110,138,139,140]. …”

“…The direct point-by-point inscription was first demonstrated in the POF core without damage using 800 nm femtosecond laser by Stecher et al in 2009 [138]. Based on this method, LPGs in mPOFs [109,110] and VA-doped SI POFs [66,76] have been fabricated. As each point will be created by the focused laser beam, the period will be limited by the diffraction limit.…”

“…So far, based on different kinds of mechanisms and writing methods, many LPGs have been fabricated in SM and MM POF, SI and GI POF, as well as mPOFs as listed in Table 4 [48,67,71,72,73,75,76,78,79,82,84,87,109,110,123,135,136,138,142,147]. The point-by-point technique is the most used method used for POF LPG fabrication.…”

Online Tests of an Optical Fiber Long-Period Grating Subjected to Gamma Irradiation

“…As compared to FBGs, LPGs have a length of the order of centimeters against few mm in the case of FBGs, and a larger pitch of the modulation profile, in the order of hundreds of m as compared to FBGs which exhibit a period G 750 nm [3], [4]. Various techniques were used to fabricate LPGs: CO 2 lasers [2], [4], [5]; UV radiation [6]- [8]; visible [3] or UV fs laser radiation [3], [9], [10]; IR fs laser radiation [11]; electric arc discharge [8], [12], [13]; LPGs were inscribed in pure-silica-core fibers/ F-doped silica cladding [13]; SMF-28 Gedoped SiO 2 [2]- [4], [7], [9], [11], [14]; B co-doped fiber [8]; N-doped silica fibers [14]; microstructured PMMA optical fiber [6]; special optical fibers for radiation environments [15]; FORC or Fujikura telecommunication optical fiber [3]; pure fused silica photonic crystal fiber [10]; H2loaded SMF-28 [10]; Al 3þ -doped and Er 3þ =Al 3þ -codoped fibers [12]; solid-core PCFs or air-core PBFs [5]. The writing methods were either a step-by-step process [1], [2], [4], [6], [9]- [11] or amplitude mask [1], [7].…”