Positioned on a block is a filter for reflecting light 1 and
transmitting another light 2. First and second light guides are positioned
on the block in an aligned relation to each other so that their angled ends oppose
to each other. An adhesive is applied to the angled ends of the light guides for
holding a filter. Light 2 is introduced in the light guides for adjusting
the position of the light guides so that a predetermined amount of light is discharged
from the light guide. A light receiver is positioned on the block through the adhesive
and then light is introduced in the light guide for adjusting the position of the
light receiver relative so that a predetermined amount of light is received by
the light receiver. In particular, the adhesive has the same refractive index as
the light guides.
