Coupling device for coupling signals into and out of a transmission glass-fiber

An optical wavelength-division multiplexing and demultiplexing device comprising:

• first and second imaging devices, each of which can convert a point light source into parallel rays and can convert parallel rays into a point light source;
• and
• an optical grating situated between the imaging devices such that parallel rays, produced by the imaging devices from point light sources, will pass through the grating;
• CHARACTERIZED IN THAT:
• the grating is a binary transparent phase grating with a rectangular groove profile, said grating having a duty factor of 1:1;
• the grating has an optical path difference, H=(n-1)h, which is substantially given by
• H=n.sub.1 .lambda..sub.I, and
• H=(m.sub.1 +1/2).lambda.k
• where n.sub.1 and m.sub.1 are positive integers, N is the refractive index of the grating material, h is the grating height and .lambda..sub.I and .lambda..sub.k are two optical wavelengths to be multiplexed and demultiplexed;
• and
• the device further comprises a transmission optical fiber having an end located to one side of the grating at a point where light exitting the fiber will be converted, by one of the imaging devices, into parallel rays substantially perpendicular to the grating, light beams of the two optical wavelengths to be multiplexed being simultaneously passed through the optical fiber in opposite directions.