Multi-fiber digital delay line

• US 6,351,587 B1
• Filed: 11/12/1999
• Issued: 02/26/2002
• Est. Priority Date: 11/12/1999
• Status: Expired due to Term

• Current Assignee: Furukawa Electric North America Incorporated (Furukawa Electric Company Limited)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Holland, William Robert
• Primary Examiner(s): NGO, HUNG NHAT
• Application Number:
  US09/439,886
• Time in Patent Office: 837 Days
• Field of Search: 385/24, 385/27, 385/48
• US Class Current: 385/48
• CPC Class Codes: G02B 6/2861 using fibre optic delay lines and optical elements associated with them, e.g. for use in signal processing, e.g. filtering delay lines in general H03H, H01P9/00; optical computing devices G06E
• CPC Class Codes: G02B 6/3608 Fibre wiring boards, i.e. where fibres are embedded or attached in a pattern on or to a substrate, e.g. flexible sheets optical ribbon cables in support members G02B6/4401
• CPC Class Codes: G02B 6/444 Systems or boxes with surplus lengths

Abstract

A multi-fiber optical delay line incorporates a plurality of optical fibers nestedly positioned and affixed to a planar substrate. The fibers include input portions that are linearly and proximately positioned on the substrate, and of equivalent length. The fibers also include output portions that are linearly and proximately positioned on the substrate, and of equivalent length. The input and output portions of each fiber are interconnected by a u-shaped connecting portion, and each connecting portion is positioned to have a unique and predetermined length. The predetermined lengths are selected such that differences in length between a shortest fiber and another fiber in the plurality of fibers are equivalent to a fiber length that would be traversed by the input signal during a time period required for the transmission of a predetermined number of bits in the digital signal. The input portions of the fibers are coupled to an optical splitter which provides one copy of an input signal substantially simultaneously to each of the input portions. In a preferred embodiment of the invention, a planar heater and overcoating are used to control the thermal profile across the plurality of fibers.

Claims

1. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

wherein each fiber includes one or more fiber segments,

wherein the one or more fiber segments include;

an input segment, wherein the input segment includes the input end, and individual ones of the input segments for the plurality of optical fibers are collectively and co-linearly positioned substantially in the single physical plane so that the input ends of the individual ones of the input segments lie on a line substantially perpendicular to the individual ones of the co-linear input segments;

an output segment, wherein the output segment includes the output end, and individual ones of the output segments for the plurality of optical fibers are collectively and co-linearly positioned substantially in the single physical plane so that the output ends of the individual ones of the output segments lie on a line substantially perpendicular to the individual ones of the co-linear output segments; and

a connecting segment, wherein individual ones of the connecting segments for the plurality of optical fibers are collectively and nestedly positioned in the single physical plane,

wherein ones of the plurality of input segments have substantially equivalent optical lengths, ones of the plurality of output segments have substantially equivalent optical lengths and each of the plurality of connecting segments has a unique predetermined optical length.

2. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

wherein each fiber includes one or more fiber segments,

wherein the one or more fiber segments include;

an input segment, wherein the input segment includes the input end, and individual ones of the input segments for the plurality of optical fibers are collectively and co-linearly positioned substantially in the single physical plane so that the input ends of the individual ones of the input segments lie on a line substantially perpendicular to the individual ones of the co-linear input segments;

an output segment, wherein the output segment includes the output end, and individual ones of the output segments for the plurality of optical fibers are collectively and co-linearly positioned substantially in the single physical plane so that the output ends of the individual ones of the output segments lie on a line substantially perpendicular to the individual ones of the co-linear output segments; and

a connecting segment, wherein individual ones of the connecting segments for the plurality of optical fibers are collectively and nestedly positioned in the single physical plane,

wherein each of the plurality of input segments has a unique predetermined optical length, each of the plurality of output segments has a unique predetermined optical length and ones of the plurality of connecting segments have substantially equivalent optical lengths.

3. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

wherein each fiber includes one or more fiber segments,

wherein the one or more fiber segments include a singular segment, the singular segment being u-shaped and including the input end and the output end, and wherein singular segments for each of the plurality of optical fibers each have a unique predetermined optical length.

4. The delay line of claim 3, wherein input ends for each of the plurality of optical fibers lie substantially on a first line and output ends for each of the plurality of optical fibers lie substantially on a second line.

5. The delay line of claim 4, wherein the first line and the second line extend to form a single line.

6. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

wherein a difference d between the predetermined optical length of a first one of the plurality of optical fibers and the predetermined optical length of a second one of the plurality of optical fibers is equivalent to an optical length that would be traversed by a digital optical input signal during a time period required for the transmission of a predetermined number of bits in the digital optical input signal.

7. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

wherein the nested position of the plurality of optical fibers is maintained in the single plane by bonding said plurality of optical fibers to a first planar surface of a substrate.

8. The delay line of claim 7, wherein the substrate comprises a rigid, dimensionally stable material.

9. The delay line of claim 8, wherein the material is selected from the group consisting of MYLAR, glass epoxy and polyimide.

10. The delay line of claim 7, further comprising a planar heater affixed to a second planar surface of the substrate.

11. The delay line of claim 10, wherein said planar heater is selectively energized to establish a predetermined, stable thermal profile in the plurality of optical fibers such that drift and jitter in the optical fibers are substantially eliminated.

12. The delay line of claim 11, wherein said planar heater is a thin film heater.

13. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

further comprising an optical combiner for combining the input signal copies arriving at the output ends of the plurality of optical fibers to form a single output signal.

14. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

wherein each fiber includes one or more fiber segments,

wherein the one or more fiber segments include;

an input segment, wherein the input segment includes the input end, and individual ones of the input segments for the plurality of optical fibers are collectively and co-linearly positioned substantially in the single physical plane so that the input ends of the individual ones of the input segments lie on a line substantially perpendicular to the individual ones of the co-linear input segments;

an output segment, wherein the output segment includes the output end, and individual ones of the output segments for the plurality of optical fibers are collectively and co-linearly positioned substantially in the single physical plane so that the output ends of the individual ones of the output segments lie on a line substantially perpendicular to the individual ones of the co-linear output segments; and

a connecting segment, wherein individual ones of the connecting segments for the plurality of optical fibers are collectively and nestedly positioned in the single physical plane,

wherein the nested optical fibers are further concentrically wound into a coil, such that the input segments and the output segments of the nested optical fibers proximately project from a circumference of the concentric coil.

15. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

wherein each fiber includes one or more fiber segments,

wherein the one or more fiber segments include;

an input segment, wherein the input segment includes the input end, and individual ones of the input segments for the plurality of optical fibers are collectively and co-linearly positioned substantially in the single physical plane so that the input ends of the individual ones of the input segments lie on a line substantially perpendicular to the individual ones of the co-linear input segments;

an output segment, wherein the output segment includes the output end, and individual ones of the output segments for the plurality of optical fibers are collectively and co-linearly positioned substantially in the single physical plane so that the output ends of the individual ones of the output segments lie on a line substantially perpendicular to the individual ones of the co-linear output segments; and

a connecting segment, wherein individual ones of the connecting segments for the plurality of optical fibers are collectively and nestedly positioned in the single physical plane,

wherein the connecting segment of at least one optical fiber further includes one or more concentric loops, the concentric loops being substantially positioned in the single plane and bonded to the substrate surface.

16. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

wherein the plurality of optical fibers are multimode fibers.

17. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

wherein individual ones of the input segments are spaced at a standard pitch so that a first uniform distance between a central axis of a first input segment and a central axis of an adjacent input segment is between 100 and 105 percent of a diameter of the first fiber.

18. An optical delay line capable of receiving an optical input signal and of outputting a plurality of copies of the input signal that are delayed in time with respect to each other, the delay line comprising:

a plurality of optical fibers each having an input end, and positioned substantially in a single physical plane and in nested relation each to the others such that each of the plurality of optical fibers has a unique predetermined optical length; and

an optical splitter arranged to produce a plurality of copies of the input signal and provide one copy of the input signal substantially simultaneously to each one of the plurality of input ends;

whereby each of the plurality of copies traverses a particular one of the plurality of optical fibers over a unique interval in time to arrive at an output end of the particular one of the fibers, the unique time interval being related to the predetermined optical length of the particular one of the fibers,

wherein individual ones of the output segments are spaced at a standard pitch so that a first uniform distance between a central axis of a first output segment and a central axis of an adjacent output segment is between 100 and 105 percent of a diameter of the first fiber.