Fiber optic switch and discretely variable delay line

A method of making a tapped delay line with a discretely variable time delay, said method comprising:

• providing first and second single mode optical fibers;
• removing a portion of the cladding from plural selected locations along said first fiber to provide respective plural evanescent field coupling regions;
• removing a portion of the cladding from a selected location along said second fiber to provide an evanescent field coupling region;
• and
• adjustably mounting said fibers for selective juxtaposition of said second fiber coupling region and any one of said plural first fiber coupling regions.

A fiber optic frequency filter, comprising:

• a first single mode optical fiber, a portion of which includes plural taps, spaced at predetermined intervals along said first fiber portion;
• a second single mode optical fiber;
• first means for optically coupling said second fiber to a selected one of said plural taps of said first fiber at a first predetermined location on said second fiber;
• second means for optically coupling said first and second fibers at a first predetermined location on said first fiber, removed from said first fiber portion, and at a second predetermined location on said second fiber;
• and
• means for adjusting said first means for optically coupling to couple said fibers at another of said plural taps to vary the frequency response of said filter.

A method of frequency filtering, comprising:

• providing first and second single mode optical fibers each having a core and a cladding, a portion of said first fiber having plural taps, spaced at predetermined intervals along said first fiber and said first fiber having a first tap, the cladding at each of the taps on said first and second fiber being sufficiently thin on at least one side thereof to tap light therefrom;
• relatively positioning said optical fibers to provide optical coupling between said first and second fibers at one of said plural taps on said second fiber and at said first tap of said first fiber;
• an optical coupler coupling said first fiber to said second fiber at a predetermined location removed from said plural taps;
• introducing a modulated light wave into one of said single mode fibers to provide an optical output signal in the other of said single mode fibers, said output signal comprised of light modulated at first and second frequencies;
• and
• relatively positioning said first and second optical fibers to provide optical coupling at another of said plural taps selected to pass the portion of said optical output signal at said first frequency, while attenuating the portion of said optical output signal at said second frequency.

A fiber optic switch, comprising:

• a set of plural strands of single mode optical fiber, each of said strands having an evanescent field coupling region;
• a strand of optical fiber, separate from said set of plural strands, having an evanescent field coupling region;
• and
• means for relatively positioning said optical fiber strand and said set of plural strands to selectively juxtapose said evanescent field coupling region of said optical fiber strand with a selected one of said evanescent field coupling regions of said set of plural strands, to selectively couple optical power between said fiber strand and one of said plural fiber strands.