Claims
- 1. An optical star coupler formed as a taper comprising:
- an input, single mode fibre;
- at least three identical output, single mode fibres, forming an output fibre assembly with each output fibre being positioned substantially identical relative to the remaining output fibres throughout the taper, wherein fundamental mode fields of the input fibre and output fibre assembly are substantially matched in some region of the taper.
- 2. A method of forming a 1.times.N optical star coupler having an input, single mode fibre and N identical output, single mode fibres, where N is greater than or equal to three, comprising the steps of:
- (a) forming N+1 fibre portions each having a single mode optical fibre fusion spliced to a coreless fibre;
- (b) placing the N+1 fibre portions into a former such that the N output, single mode fibres extend as a ring from one end of the former, each positioned substantially identically relative to the remaining fibres in the ring with one single mode input fibre extending from the other end of the former, and all fusion splices being in substantially the same plane; and
- (c) forming a taper such that fundamental mode fields on each side of the fusion splices are substantially matched in some region of the taper.
- 3. A method of forming a 1.times.N optical star coupler where N is greater than or equal to three, comprising the steps of:
- (a) inserting N identical single mode fibres into a former so as to extend from the same side of the former, each being positioned substantially identically relative to the remaining fibres;
- (b) forming a taper with a waist diameter substantially equal to the diameter of a single fibre;
- (c) cleaving the taper at the waist;
- (d) fusion splicing the cleaved taper to a single mode input fibre; and
- (e) further tapering the taper to equalise the field modes on either side of the splice.
- 4. A method of forming a coupler as claimed in either of claims 2 or 3 in which the insertion of the fibres into the former is lubricated.
- 5. A method of forming a coupler as claimed in claim 4, wherein the former is lubricated using methanol.
- 6. A method of forming a coupler as claimed in claim 2 or 3 in which equalisation of the field modes is determined by tapering until maximum power transmission from the the input fibre is obtained.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 8816521 |
Jul 1988 |
GBX |
|
Parent Case Info
The invention relates to optical couplers, and in particular to couples for disturbing light from one single mode optical fibre between two or more single mode optical fibres.
It is an object of the present invention to provide an optical coupler in which the light is transferred equally from the one single mode fibre to the other fibres independently of wavelength.
According to a first aspect the present invention comprises an optical star coupler formed as a taper having an input, single mode fibre and at least three identical output, single mode fibres, which output fibres form an output fibre assembly characterised in that each of the output fibres is positioned substantially identically relative to the remaining output fibres throughout the taper, the fundamental mode fields of the input fibre and output fibre assembly being substantially matched at some region of the taper.
The positions of the fibres ensure that the output fibres are illuminated with the same optical field amplitude and phase and because the distribution of fibres around a given output fibre is identical to that around any other there is zero net power transfer between the array of output fibres.
To produce a low loss device, there must be a gradual change in the mode field from that of the single input fibre to that of the output fibres. This mode transformation is accomplished by means of the taper. The space between the fibre array must first be filled with material of the same or slightly lower refractive index than that of the fibre cladding. This filling material is conveniently the same material as the cladding, for example silica.
According to a second aspect of the present invention a method of forming a 1.times.N optical star coupler having an input, single mode fibre and N identical output, single mode fibres where N is greater than or equal to three characterised in including the steps of:
(a) forming N+1 fibre portions each comprising a single mode optical fibre fusion spliced to a coreless fibre;
(b) placing the N+1 fibre portions into a former such that the N output, single mode fibres extend as a ring from one end of the former each positioned substantially identically relative to the remaining fibres in the ring, and one single mode input fibre extends from the other end of the former; all the fusion splices being in substantially the same plane;
(c) forming a taper such that the fundamental mode fields on each side of the fusion splices are substantially matched at some region of the taper.
PCT Information
| Filing Document |
Filing Date |
Country |
Kind |
102e Date |
371c Date |
| PCT/GB89/00769 |
7/6/1989 |
|
|
1/10/1991 |
1/10/1991 |
| Publishing Document |
Publishing Date |
Country |
Kind |
| WO90/00751 |
1/25/1990 |
|
|
US Referenced Citations (9)
Foreign Referenced Citations (9)
| Number |
Date |
Country |
| 1212083 |
Nov 1986 |
AUX |
| 0013972 |
Aug 1980 |
EPX |
| 0198761 |
Oct 1986 |
EPX |
| 0212954 |
Mar 1987 |
EPX |
| 55-127502 |
Dec 1980 |
JPX |
| 57-186730 |
Feb 1983 |
JPX |
| 58-153916 |
Dec 1983 |
JPX |
| 61-28908 |
Jun 1986 |
JPX |
| 2199423 |
Jul 1988 |
GBX |
Non-Patent Literature Citations (2)
| Entry |
| Electronics Letters, vol. 22, No. 6, Mar. 13, 1986, Mortimore et al., "Low loss joints between dissimilar fibers by tapering," etc. pp. 318-319. |
| Electronics Letters, vol. 23, No. 20, Sep. 24, 1987, Minelly et al., "Single-mode fibre Y-junction beam splitter", pp. 1087-1088. |
Patent Grant
5129021
