Question

Graded-index plastic optical fibre (GI POF) is expected to be used for high- speed local area networks (LANS) because of its large core which allows for low cost and easy installation. A particular GI POF has a core diameter of 200um, a maximum core index of 1.500 and a numerical aperture of 0.30. 2.c.i 2.c.ii What is the maximum acceptance angle for this fibre? [2 marks] What is the refractive index of the cladding material for this fibre? 12 marks/ 2.c.iii What is the maximum internal angle which a guided ray of light makes with the fibre axis? [2 marks) 2.d Light at a wavelength of 1.3um is propagating in a single-mode fibre with a core diameter of 8um. The intensity of the guided mode is measured to have a ller width of 3.5um. What is the modal spot size, 0o, for this mode? [2 marks]

Answer 1

Qui Max * core Prolex = 1.5 Nr. A0.30 core diameter 200lum in Maxm acceptance angle sinda = 57,2-122 N.A. Das sin ( 0-30) 17.4571 N. A J ned) -n2² 0.3 : 1 (115)2-n, 2 : 1. n2=1.469 DA deternal "") Oc critical angle for total reflection so Oc = sin- (1.469 )= 78-33 lo angle with fiber axis ! :90-78.33 - 11.67A