SIGNAL DETECTION AND DELAY EQUALIZATION IN OPTICAL FIBER TRANSMISSION SYSTEMS

• US 3,777,149 A
• Filed: 07/17/1972
• Issued: 12/04/1973
• Est. Priority Date: 07/17/1972
• Status: Expired due to Term

• Current Assignee: Enrique Alfredo Jose Marcatili
• Original Assignee: Enrique Alfredo Jose Marcatili
• Inventors: Marcatili, Enrique Alfredo Jose
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Grigsby, T. N.
• Application Number:
  US05/272,371
• Time in Patent Office: 505 Days
• Field of Search: 350/96WG 250/227,209,208 333/95
• US Class Current: 250/208.6
• CPC Class Codes: G02B 6/14 Mode converters
• CPC Class Codes: G02B 6/268 for modal dispersion control, e.g. concatenation of light guides having different modal dispersion properties graded index multimode fibres G02B6/0288; multimodal transmission systems H04B10/2581
• CPC Class Codes: G02B 6/2852 using tapping light guides arranged sidewardly, e.g. in a non-parallel relationship with respect to the bus light guides (light extraction or launching through cladding, with or without surface discontinuities, bent structures)
• CPC Class Codes: G02B 6/4206 Optical features G02B6/4207, G02B6/421 take precedence
• CPC Class Codes: G02B 6/4215 the intermediate optical elements being wavelength selective optical elements, e.g. variable wavelength optical modules or wavelength lockers G02B6/4246 takes precedence
• CPC Class Codes: G02B 6/4249 comprising arrays of active devices and fibres
• CPC Class Codes: G02B 6/425 Optical features semiconductor laser arrays H01S5/40; hybrid LED arrays H01L25/0753; monolithic LED arrays H01L27/153

Abstract

A stripper at the end of an optical fiber selectively couples propagating signal components out of the fiber at characteristic angles. A linear array of photodetectors selectively responds to each of the coupled signal components or to groups of such components. When used simply as a mode or as a frequency separator, the detected signals are separately coupled to different output circuits. In a detector-equalizer embodiment, the signals, suitably delayed relative to each other, are coupled to a common output circuit.

Claims

1. A signal detector arrangement for use with an optical fiber waveguide having an inner core and outer cladding, including:

a stripper for coupling wave Energy out of said fiber, comprising a slab of dielectric material in coupling relationship with said core, where the refractive index of said material is equal to or greater than the index of said core; and

an array of photodetectors disposed adjacent to said stripper where each photodetector is dimensioned and oriented to intercept wave energy coupled out of said fiber within a different range of angles.

2. The arrangement according to claim 1 wherein said fiber is a multimode waveguide;

and wherein each detector intercepts wave energy associated with one of the modes guided along said fiber, or with a selected group of said modes.

3. The arrangement according to claim 1 wherein said fiber is a single mode waveguide;

and wherein each detector intercepts different frequency wave energy.

4. The arrangement according to claim 1 wherein each of said detectors is coupled to an output circuit.

5. The arrangement according to claim 1 including a common output circuit;

and means for coupling each of said detectors to said common output circuit.

6. The arrangement according to claim 5 wherein said coupling means includes delay networks for compensating for the delay distortion produced in said fiber.

7. The arrangement according to claim 1 wherein each of said photodetectors is a Schottky barrier photodiode.

8. The arrangement according to claim 2 including means for focusing the wave energy associated with a different one of said modes, or with a different selected group of said modes onto each of said photodetectors;

and wherein said photodetectors are located at the focal plane of said focusing means for said different modes.

9. A detector-equalizer for use with a multimode optical fiber waveguide comprising:

a signal detector arrangement in accordance with claim 1;

a common output circuit; and

means including delay networks for coupling the output signals from said array of photodetectors to said output circuit to minimize the delay distortion introduced by said fiber.

10. The detector-equalizer according to claim 9 wherein the means for coupling the output signals from the photodetectors responsive to the faster propagating modes include delay networks for equalizing the total average delay for all of said groups of modes.

11. The detector-equalizer according to claim 8 wherein said coupling means include signal amplifiers.