CA1105752A - Coupler for multimode single fiber optics data links - Google Patents
Coupler for multimode single fiber optics data linksInfo
- Publication number
- CA1105752A CA1105752A CA330,139A CA330139A CA1105752A CA 1105752 A CA1105752 A CA 1105752A CA 330139 A CA330139 A CA 330139A CA 1105752 A CA1105752 A CA 1105752A
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- Prior art keywords
- fiber
- coupler
- optical
- region
- point
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Abstract
ABSTRACT OF THE DISCLOSURE
There is disclosed an optical coupler for coupling optical energy to or from optical fibers. The coupler comprises an optically transparent cylinder in which there is located a biconical tapered section and at least one parallely adjacent single tapered section whose taper is selectively positioned with respect to the mid-point of the biconical section.
There is disclosed an optical coupler for coupling optical energy to or from optical fibers. The coupler comprises an optically transparent cylinder in which there is located a biconical tapered section and at least one parallely adjacent single tapered section whose taper is selectively positioned with respect to the mid-point of the biconical section.
Description
7~iZ
This invention relates ~enerally to means for coupling energy propagating in optical flbers and More particularly to a multi-port coupler therefor.
For applications that require bidirectional communications over a single multi-mode optical fiber such as fiber optic payout systems, there is an explicit need for a bidirectional coupler that can provide low levels of near end back scatter, effectively excite the single multi-mode fiber, and - be economically manufactured and effectively ruggedized.
The coupler of the present invention is based on a well known physical concept that an optical fiber which is longitudinally tapered will exhibit conversion of guided modes into radiation modes. As the core of the fibers is reduced in size from its nominal diameter, the highest order mode will be cut off first and converted to radiationO As the core is made smaller and smaller, more and more of the lower order modes are radiated.
F mally, for core sizes below a prescribed value, only the lowest order mode will remain in the fiber. If the tapered fIber is surrounded by an optically transparent cylinder larger than the fiber, the radiated energy will become trapped within this outer cylinder. The process of converting the fiber guided modes by wave rad~ation to the guided modés of the transparent cylinder can be reversed by reversing the taper of the fiber.
If the fiber is tapered down to a waist region and then back to its original size, there is provided what is called a biconical taper and higher modes will leak out and be trapped in the outer cylinder which eventually are relaunched into the fiber on the other side oi the waist region. If two or more biconically tapered fibers are placed parallel and in close proximity .. . .
within the transparent cylinder, the modes which are created in that cylinder ; will be recoupled back into the fibers. A four port coupler is thus provided.~ Such a device is disclosed in an article entitled "Optical ~Directional Coupler Using Tapered Sections In Multi-Mode Fibers", by T. Ozeki, et al. which appeared in the Applied Physics Letters, VolO 28, No. 9, May, 1976 at pages 528, 529. Additionally in another article en~itled i :
" . , "Full Duplex Transmission Link Over Single-Strand Optical ~iber", by B.S. Kawasaki, et al. appeared at Optical Letters,Vol. 1, I~O. 3, September, 1977., at pages 107, 108, there is also disclosed a biconically tapered coupler having twin biconical sections wherein one unused port is terminated remotely from the side fusion region by tapering the fiber to a point and inserting the end in a small tube of oil which is carefully index matched to the fiber material.
Briefly, the subject invention is described to a multi-port and, in one configuration a three port coupler, including an optically trans-parent cylinder in which there is located a biconically tapered section and at least one parrallel adjacent single tapered secti.on whose taper is selectively positioned with respect to the waist region of the biconical section. In another configuration of the invention a plurality of single tapered sections are arranged in an encircling relationship with one section of the biconical section adjacent its waist region.
Figure 1 is a diagram illustrative of the conversion of optical energy from guided modes into radia~ion modes which in turn couple into guided modes of the cylinder;
Figure 2 is a diagram illustravtive of optical energy being converted Erom radiation modes which are guided modes of the cylinder to guided modes of the Eiber;
Figure 3 is a diagram illustrative of both types of conversion by means of a biconical taper section located within an optically transparent cyl~nder;
Figure 4 is a diagram illustrative of a four port coupler of known prior art design;
Figure 5 is a diagram illustrative of a first embodlment of the subject invention;
Figure 5 is a diagram illustrative of a second embodiment of the ; 30 subject invention;
Figure 7 is a diagram illustrative of a third embodiment of the subject invention; and
This invention relates ~enerally to means for coupling energy propagating in optical flbers and More particularly to a multi-port coupler therefor.
For applications that require bidirectional communications over a single multi-mode optical fiber such as fiber optic payout systems, there is an explicit need for a bidirectional coupler that can provide low levels of near end back scatter, effectively excite the single multi-mode fiber, and - be economically manufactured and effectively ruggedized.
The coupler of the present invention is based on a well known physical concept that an optical fiber which is longitudinally tapered will exhibit conversion of guided modes into radiation modes. As the core of the fibers is reduced in size from its nominal diameter, the highest order mode will be cut off first and converted to radiationO As the core is made smaller and smaller, more and more of the lower order modes are radiated.
F mally, for core sizes below a prescribed value, only the lowest order mode will remain in the fiber. If the tapered fIber is surrounded by an optically transparent cylinder larger than the fiber, the radiated energy will become trapped within this outer cylinder. The process of converting the fiber guided modes by wave rad~ation to the guided modés of the transparent cylinder can be reversed by reversing the taper of the fiber.
If the fiber is tapered down to a waist region and then back to its original size, there is provided what is called a biconical taper and higher modes will leak out and be trapped in the outer cylinder which eventually are relaunched into the fiber on the other side oi the waist region. If two or more biconically tapered fibers are placed parallel and in close proximity .. . .
within the transparent cylinder, the modes which are created in that cylinder ; will be recoupled back into the fibers. A four port coupler is thus provided.~ Such a device is disclosed in an article entitled "Optical ~Directional Coupler Using Tapered Sections In Multi-Mode Fibers", by T. Ozeki, et al. which appeared in the Applied Physics Letters, VolO 28, No. 9, May, 1976 at pages 528, 529. Additionally in another article en~itled i :
" . , "Full Duplex Transmission Link Over Single-Strand Optical ~iber", by B.S. Kawasaki, et al. appeared at Optical Letters,Vol. 1, I~O. 3, September, 1977., at pages 107, 108, there is also disclosed a biconically tapered coupler having twin biconical sections wherein one unused port is terminated remotely from the side fusion region by tapering the fiber to a point and inserting the end in a small tube of oil which is carefully index matched to the fiber material.
Briefly, the subject invention is described to a multi-port and, in one configuration a three port coupler, including an optically trans-parent cylinder in which there is located a biconically tapered section and at least one parrallel adjacent single tapered secti.on whose taper is selectively positioned with respect to the waist region of the biconical section. In another configuration of the invention a plurality of single tapered sections are arranged in an encircling relationship with one section of the biconical section adjacent its waist region.
Figure 1 is a diagram illustrative of the conversion of optical energy from guided modes into radia~ion modes which in turn couple into guided modes of the cylinder;
Figure 2 is a diagram illustravtive of optical energy being converted Erom radiation modes which are guided modes of the cylinder to guided modes of the Eiber;
Figure 3 is a diagram illustrative of both types of conversion by means of a biconical taper section located within an optically transparent cyl~nder;
Figure 4 is a diagram illustrative of a four port coupler of known prior art design;
Figure 5 is a diagram illustrative of a first embodlment of the subject invention;
Figure 5 is a diagram illustrative of a second embodiment of the ; 30 subject invention;
Figure 7 is a diagram illustrative of a third embodiment of the subject invention; and
- 2 -7~ii2 Figure 8 is a cross sectional view of the embodiment shown in Figure 7 taken along the lines 8-8.
Figures 1 through 4 illustratively provide the background for the subject invention and constitute known prior art concepts and devices.
Figure 1, for example, discloses an optical wave-guide in the form of a fiber 10 which has optical energy 12 inputted thereto and which is transmitted in guided modes up to the region 14 where the fiber 10 is long-itudinally tapered to a pointO The region 14 at least is surrounded by an optically transparent cylinder 16 which is larger in cross section than the fiber itself. The optical energy transmitted through the riber 10 at the tapered region 14 will be converted from a guided mode into radiation modes. As the cross sectional diameter of the fiber is reduced in size from its nominal diameter, the highest order modes will be cut off and converted to radiation 18. As the core is made smaller and smaller, more and more of the lower order modes are radiated. Finally for core sizes below a prescribed value, only the lowest order mode will remain in the fiberO What is significant, however, is that the radiated energy 18 will be trapped as reflected energy 20 within the cylinder 16 and become guided modes of the cylinder. The reverse process is shown in Figure 2 wherein another optical fiber 22 having a tapered region 24 is located within the transparent cylinder 16. Such an arrangement will receive the reflected energy 20 and be relaunched into the fiber 22 in the form of guided modes~
As is well known, if a biconically tapered optical fiber 26 as shown in Figure 3 i8 located within the cylinder 16 and has two opposing tapered sections 28 and 30 separated by a waist region of reduced finite diameter higher order modes will be converted to radiation in tapered section 28 which will then be reflected back to the tapered secti~ 30. Proceeding now to Figure 4, there is disclosed a four port coupler in accordance with the teachings of the Ozeki, et al. pulbication referenced above. In this - 30 instance two doubly tapered or biconical fibers 34 and 35 are located in close parrallel proximity within the transparent cylinder 16 and radiation modes that are created in the cylinder 16 from energy inputted into one of 5~
the fibers are reco~le~ back into both fibers past the ,laist regions 35 and 37. For example, an optical signal fed into port 1 will be effectively split into ports 3 and 4. The optical signal coming out of port 2 will consist of back scatter, which if proper coupling coefficients exist, will be negligible. It can be seen that a device such as shown in Figure 4 is bidirectional in that any input coupled to one of the ports will be cou?led to the remaining ports, depending upon the coupling coefficients.
For certain applications, a three port coupler is required since the splitting of power into a fourth port is unwanted~ Accordingly, reference is now made to the first embodiment of the subject invention as depicted in Figure 5. There reference numeral 38 designates an optically transparent cylinder having two optical fibers 40 and 42 therein in parrallel relationship and in relatively close proximity to one another. The fiber 40 is tapered to an infinitesimal diameter or point 43 providing a single tapered section 44 while the second fiber 42 includes a biconical taper including the tapered sections 46 and 48 and having a waist region 50 of finite smaller diameter. In this embodiment, the tip 43 of the single tapered section 44 extends substantially to the mid-point of waist region 50 of the biconical fiber 42. In such a configuration, substantially all of the optical energy incident into port 1 will emerge through port 3, while the ; back scatter output of port 2 is substantially zero i.eO less than 20db below the input power. When a signal, however, is inputted to port 3, a splitting of power into ports 1 and 2 occurs, and if the point 43 extends laterally to substantially the mid-point of the waist region 50 as shown in Figure 5, a substantially equal splitting of output energy will occur between ports 1 and 2.
- Variations in the values of the coupling coefficients for power incident to port 3 being coupled to ports 1 and 2 can be obtained by laterally displacing the single tapered fiber 40 away from the mid-point of the waist region 50 of the biconical tapered fiber 42 as shown in Figure 6.
Ihis type of configuration allows more power to be trapped by the tapered region 46 of the biconical fiber 42 before the effect of the single tapered .
~ - 4 ~
region 44 of the fiber 40 is realized.
Proceeding now to the embodiment shown in Figure 7 and 8, whereas in the first embodiment one single tapered fiber 40 was utilized in combination with the biconical tapered fiber 42, in the present embodiment three single tapered fibers 40, 40' and 40" are located symmetrically around fiber 42 providing ports lA, lB and lC surrounding port 2 with port
Figures 1 through 4 illustratively provide the background for the subject invention and constitute known prior art concepts and devices.
Figure 1, for example, discloses an optical wave-guide in the form of a fiber 10 which has optical energy 12 inputted thereto and which is transmitted in guided modes up to the region 14 where the fiber 10 is long-itudinally tapered to a pointO The region 14 at least is surrounded by an optically transparent cylinder 16 which is larger in cross section than the fiber itself. The optical energy transmitted through the riber 10 at the tapered region 14 will be converted from a guided mode into radiation modes. As the cross sectional diameter of the fiber is reduced in size from its nominal diameter, the highest order modes will be cut off and converted to radiation 18. As the core is made smaller and smaller, more and more of the lower order modes are radiated. Finally for core sizes below a prescribed value, only the lowest order mode will remain in the fiberO What is significant, however, is that the radiated energy 18 will be trapped as reflected energy 20 within the cylinder 16 and become guided modes of the cylinder. The reverse process is shown in Figure 2 wherein another optical fiber 22 having a tapered region 24 is located within the transparent cylinder 16. Such an arrangement will receive the reflected energy 20 and be relaunched into the fiber 22 in the form of guided modes~
As is well known, if a biconically tapered optical fiber 26 as shown in Figure 3 i8 located within the cylinder 16 and has two opposing tapered sections 28 and 30 separated by a waist region of reduced finite diameter higher order modes will be converted to radiation in tapered section 28 which will then be reflected back to the tapered secti~ 30. Proceeding now to Figure 4, there is disclosed a four port coupler in accordance with the teachings of the Ozeki, et al. pulbication referenced above. In this - 30 instance two doubly tapered or biconical fibers 34 and 35 are located in close parrallel proximity within the transparent cylinder 16 and radiation modes that are created in the cylinder 16 from energy inputted into one of 5~
the fibers are reco~le~ back into both fibers past the ,laist regions 35 and 37. For example, an optical signal fed into port 1 will be effectively split into ports 3 and 4. The optical signal coming out of port 2 will consist of back scatter, which if proper coupling coefficients exist, will be negligible. It can be seen that a device such as shown in Figure 4 is bidirectional in that any input coupled to one of the ports will be cou?led to the remaining ports, depending upon the coupling coefficients.
For certain applications, a three port coupler is required since the splitting of power into a fourth port is unwanted~ Accordingly, reference is now made to the first embodiment of the subject invention as depicted in Figure 5. There reference numeral 38 designates an optically transparent cylinder having two optical fibers 40 and 42 therein in parrallel relationship and in relatively close proximity to one another. The fiber 40 is tapered to an infinitesimal diameter or point 43 providing a single tapered section 44 while the second fiber 42 includes a biconical taper including the tapered sections 46 and 48 and having a waist region 50 of finite smaller diameter. In this embodiment, the tip 43 of the single tapered section 44 extends substantially to the mid-point of waist region 50 of the biconical fiber 42. In such a configuration, substantially all of the optical energy incident into port 1 will emerge through port 3, while the ; back scatter output of port 2 is substantially zero i.eO less than 20db below the input power. When a signal, however, is inputted to port 3, a splitting of power into ports 1 and 2 occurs, and if the point 43 extends laterally to substantially the mid-point of the waist region 50 as shown in Figure 5, a substantially equal splitting of output energy will occur between ports 1 and 2.
- Variations in the values of the coupling coefficients for power incident to port 3 being coupled to ports 1 and 2 can be obtained by laterally displacing the single tapered fiber 40 away from the mid-point of the waist region 50 of the biconical tapered fiber 42 as shown in Figure 6.
Ihis type of configuration allows more power to be trapped by the tapered region 46 of the biconical fiber 42 before the effect of the single tapered .
~ - 4 ~
region 44 of the fiber 40 is realized.
Proceeding now to the embodiment shown in Figure 7 and 8, whereas in the first embodiment one single tapered fiber 40 was utilized in combination with the biconical tapered fiber 42, in the present embodiment three single tapered fibers 40, 40' and 40" are located symmetrically around fiber 42 providing ports lA, lB and lC surrounding port 2 with port
3 being located on the other side of the waist region SO. In such an embodiment, input energy coupled to ports LA, lB and lC will be combined and will exit out of port 3. In the other direction, optical energy coupled to port 3 will be coupled to ports LA, lB and lC as well as port 2 depending upon the lateral displacement of the tapered regions 40, 40' and 40" with respect to the mid-point of the waist region 50 of the biconical tapered fiber 42. The embodiment shown in Figures 7 and 8 is particularly adapted for combining the optical power generated from three strips of a triple stripe injection laser.
Thus what has been shown and described is an improved bi-directional optical power coupler consisting of a combination of a biconical tapered section and a single tapered section located within a common optically transparent cylinder.
Thus what has been shown and described is an improved bi-directional optical power coupler consisting of a combination of a biconical tapered section and a single tapered section located within a common optically transparent cylinder.
Claims (7)
- THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
l. A bi-directional optical coupler for coupling optical energy between optical fibers comprising in combination:
an internally reflective body adapted to reflect radiation modes of optical energy which have been converted from guided modes;
a first single port optical fiber having a nominal diameter terminating in said body as a single longitudinal tapered section converging substantially to a point; and a second optical fiber located in said body, having respective ports at either end and including a pair of intermediate tapered conical sections joined to a region of reduced diameter, said first and second optical fibers being located and adjacent one another with the point of said first optical fiber being selectively positioned relative to the region of reduced diameter between said tapered regions of said second fiber. - 2. The coupler as defined by claim 1 wherein said internally reflective body comprises an optically transparent cylinder.
- 3. The coupler as defined by claim 1 wherein said point of said first optical fiber extends laterally to substantially the mid-point of said region of reduced diameter of said second fiber.
- 4. The coupler as defined by claim l wherein said point of said first fiber is displaced laterally a predetermined distance away from the mid-point of said region of reduced diameter of said second fiber.
- 5. The optical coupler as defined by claim l and additionally including at least one additional optical fiber like said first recited single port optical fiber and whereby said two like single port optical fibers are located parallely adjacent said second optical fiber in the region of one tapered section thereof.
- 6. The coupler as defined by claim 5 wherein said two like optical fibers have tapered end points which are laterally displaced away from the mid-point of said region of reduced diameter of said second fiber.
- 7. The coupler as defined by claim 1 and additionally including two more optical fibers like said first recited single port optical fiber, and all of said like single port optical fibers being positioned parallely around and adjacent a common region of said second optical fiber inside said internally reflective body.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US94797278A | 1978-10-02 | 1978-10-02 | |
| US947,972 | 1978-10-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1105752A true CA1105752A (en) | 1981-07-28 |
Family
ID=25487054
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA330,139A Expired CA1105752A (en) | 1978-10-02 | 1979-06-15 | Coupler for multimode single fiber optics data links |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1105752A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4728170A (en) * | 1984-05-11 | 1988-03-01 | Standard Telephones And Cables Public Limited Co. | Single mode optical fibre attenuators |
-
1979
- 1979-06-15 CA CA330,139A patent/CA1105752A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4728170A (en) * | 1984-05-11 | 1988-03-01 | Standard Telephones And Cables Public Limited Co. | Single mode optical fibre attenuators |
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |