Optical fiber

DETAILED DESCRIPTION A primary object of the present invention is to provide an optical fiber having a wide transmission bandwidth which may be suitably used for video transmission and which has a large product of transmission bandwidth and transmission distance.
To effectively accomplish the abovementioned object, the present invention provides an optical waveguide having a three-layer construction (hereinafter referred to as a W-type optical fiber) which comprises a first transparent dielectric center layer having a relatively high refractive index n.
sub.
o, a second transparent dielectric intermediate layer having a relatively low refractive index qn.
sub.
o and a third transparent dielectric cladding layer having an intermediate refractive index pn.
sub.
o, whereby the parameter of the optical fiber is determined as follows.
##EQU3## where B is the bandwidth of the signal to be transmitted, z is the transmission distance, namely, the fiber length, C is the velocity of light in vacuum, ##EQU4## V is the normalized frequency, that is ##EQU5## (a is the core radius, .
lambda.
is the wave length of light), and U.
sub.
11 =2.
405.
In the W-type optical fiber of the above-described construction, the value of the product Bz of the width of the transmission band B and the transmission distance z becomes larger than the value of the product of the bandwidth and the transmission distance which are determined by the capacity of a terminal receiver to be located at the end of a transmission line.
Accordingly, a primary feature of the optical fiber's low transmission loss can be effectively utilized for the transmission of signals requiring a wider bandwidth.