GB2388204A - Connecting optic fibre in elastic deformation to optical device - Google Patents
Connecting optic fibre in elastic deformation to optical device Download PDFInfo
- Publication number
- GB2388204A GB2388204A GB0210053A GB0210053A GB2388204A GB 2388204 A GB2388204 A GB 2388204A GB 0210053 A GB0210053 A GB 0210053A GB 0210053 A GB0210053 A GB 0210053A GB 2388204 A GB2388204 A GB 2388204A
- Authority
- GB
- United Kingdom
- Prior art keywords
- fibre
- substrate
- optical
- support member
- angle
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/30—Optical coupling means for use between fibre and thin-film device
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/36—Mechanical coupling means
- G02B6/3628—Mechanical coupling means for mounting fibres to supporting carriers
- G02B6/3632—Mechanical coupling means for mounting fibres to supporting carriers characterised by the cross-sectional shape of the mechanical coupling means
- G02B6/3636—Mechanical coupling means for mounting fibres to supporting carriers characterised by the cross-sectional shape of the mechanical coupling means the mechanical coupling means being grooves
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/36—Mechanical coupling means
- G02B6/3628—Mechanical coupling means for mounting fibres to supporting carriers
- G02B6/3648—Supporting carriers of a microbench type, i.e. with micromachined additional mechanical structures
- G02B6/3652—Supporting carriers of a microbench type, i.e. with micromachined additional mechanical structures the additional structures being prepositioning mounting areas, allowing only movement in one dimension, e.g. grooves, trenches or vias in the microbench surface, i.e. self aligning supporting carriers
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/36—Mechanical coupling means
- G02B6/38—Mechanical coupling means having fibre to fibre mating means
- G02B6/3801—Permanent connections, i.e. wherein fibres are kept aligned by mechanical means
- G02B6/3803—Adjustment or alignment devices for alignment prior to splicing
- G02B6/3805—Adjustment or alignment devices for alignment prior to splicing with a fibre-supporting member inclined to the bottom surface of the alignment means
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Mechanical Coupling Of Light Guides (AREA)
Abstract
Apparatus, for connecting an optical fibre 3 to an optical device 1, comprises a generally planar optical substrate 13 mounted on a generally planar base member 2, the optical substrate 13 having locating means thereon for locating the end of an optical fibre 3, relative to an optical device 1, on the substrate; and a fibre support member 10, for supporting the fibre 3 in a desired location relative to the substrate 13, the fibre support member 10 being mounted on the base 2 and comprising a first support surface 11 inclined to the plane of the base 2 for supporting a stripped portion of the fibre 3 at an angle r to the plane of the substrate so the fibre 3 is held in a state of elastic deformation to assist in holding the fibre 3 in contact with the locating means (without the fibre being secured thereto), the dimensions of the support member 10 and the angle r being selected so that, when the support member 10 is located in contact with said edge of the substrate and a fibre 3 secured to the first support surface 11, the elastic deformation of the fibre is automatically determined thereby and arranged to be below a pre-set magnitude.
Description
APPARATUS FOR CONNECTING AN OPTICAL FIBRE
TO AN OPTICAL DEVICE
This invention relates to apparatus for connecting an optical fibre to a device.
It is known to connect an optical fibre to an optical device by mounting the end of the fibre in a V-groove provided in the face of an optical chip in order to align the optical fibre with a waveguide on the chip. The fibre is conventionally secured in the V-groove by adhesive or solder which can cause misalignment if too much or too little adhesive or solder is used. Such apparatus also suffers from disadvantages arising during solidification of the adhesive or solder or material creep in the adhesive or solder which can both cause movement of the fibre and so disturb the alignment of the fibre with the waveguide. The arrangement described in US60759 14 seeks to overcome these problems. It provides attachment means located remote from the V-groove arranged to hold the fibre in a state of elastic deformation so the resilience of the fibre assists in holding the end of the flare in the V-groove without needing to be secured therein by adhesive or solder.
The present invention aims to provide improvements to the arrangement described in US6075914, the disclosure of which is hereby incorporated
herein. According to a first aspect of the invention, there is provided apparatus for connecting an optical fibre to an optical device, the apparatus comprising: a generally planar optical substrate mounted on a generally planar base member, the optical substrate having locating means thereon for locating the end of an optical fibre relative to an optical device on the substrate; and a fibre support member for supporting the fibre in a desired location relative to the substrate, the fibre support member being mounted on the base and
( comprising a first support surface inclined to the plane of the base for supporting a stripped portion of the fibre at an angle to the plane of the substrate so the fibre is held in a state of elastic deformation to assist in holding the fibre in contact with the locating means without the fibre being secured thereto, the dimensions of the support member and the angle being selected so that, when the support member is located in contact with said edge of the substrate and a fibre secured to the first support surface, the elastic deformation of the fibre is automatically determined thereby and arranged to be below a pre-set magnitude.
According to a second aspect of the invention, there is provided a method of connecting an optical fibre to an optical device including the following steps: forming locating means on a generally planar optical substrate for locating the end of an optical fibre relative to an optical device on the substrate; mounting the optical substrate on a generally planar base member; forming a fibre support member comprising a first support surface for supporting a stripped portion of the fibre; mounting the fibre support member on the base member in contact with an edge of the substrate; locating a fibre in a desired position on the optical substrate and the support member; and securing the fibre to the support member, the first support surface being inclined at an angle to the plane of the base member so the fibre is held in a state of elastic deformation to assist in
holding the fibre in contact with the locating means on the substrate without the fibre being secured thereto, the angle and the dimensions of the support member being selected so that, mounting of the support member in contact with said edge of the substrate automatically determines the elastic deformation of the fibre whereby this is arranged to be below a pre-set magnitude. Preferred and optional features will be apparent from the following description
and from the subsidiary claims of the specification.
The invention will now be further described, merely by way of example, with reference to the accompanying drawings, in which: Figure 1A is a schematic side view of an optical fibre held within a V-groove by mounting the fibre so it is elastically deformed whereby its resilience holds the end of the fibre in the V-groove; Figures 1B and 1C are diagrams illustrating various parameters associated with the above for use in deriving the relationships therebetween; Figure 2 is a perspective view of an alignment block used in a preferred embodiment of the invention; Figure 3 is a schematic side view of a fibre secured to a block such as that shown in Figure 2 so as to locate it within a V-groove; and Figure 4 is a perspective view of a complete package incorporating the arrangement shown in Figure 3.
Use of the arrangement described in US6075914 has highlighted potential problems associated therewith. When a fibre is held under strain for a
prolonged period of time it is susceptible to stress corrosion which can lead to failure of the fibre. Stress corrosion arises only in the presence of moisture and when there is an applied fibre strain acting upon a flaw in the fibre.
However, there is a minimum level of strain beneath which stress corrosion does not occur. Whilst optical fibres are manufactured to a standard which normally gives a very low occurrence of fracture initiation sites, the stripping of a fibre to remove the outer coating thereof (which is necessary to securely attach the fibre to an alignment block as described in US6075914) can create fracture initiation sites. Accordingly, it is desirable to minimise the length of stripped fibre under stress and preferably to keep the level of strain as low as possible and preferably under the minimum level which gives rise to stress corrosion. On the other hand, it is also desirable for the resilient strain within the fibre to be sufficient to reliably hold the fibre within the V-groove, particularly if the level of g-force (acceleration forces) to which the device may be subjected to in use is high.
In view of this, the arrangement described in US6075914 requires very accurate manufacture of the components thereof and very accurate assembly of the components. This leads to increased costs and makes the arrangement less suitable for use in the mass production of optical devices, particularly bearing in mind variations inherent in the components due to manufacturing tolerances. Moreover, it has been found that a small increase in strain of the fibre can result in a significant reduction in its expected lifetime.
For example, for a 10km length of fibre 1% proof strain tested a difference of 0.02% can result in a reduction in expected life-time from 25 years to 5 years.
In view of this, a detailed analysis of the parameters influencing the level of strain has been carried out. Figure 1 shows an optical chip 1 mounted on a base 2 and an optical fibre 3 mounted on an attachment block 6 so as to locate the end of the fibre 3 in a V-groove on the chip 1. The Figure illustrates some of the parameters involved in a fibre attachment according to US6075914. These include the following:
( - the angle between the top surface of the attachment block 6 and the horizontal. op - the perpendicular deflection of the fibre 3.
L - the horizontal distance from the block 6 to the end of the fibre 3 (in an undeflected position).
is determined in the manufacture of the block but can be affected by imperfections in the mating surfaces of the block 6 and base 2 or in the bond therebetween. Close inspection of the end of the fibre 3 within the V-groove reveals that the contact therebetween is not as one would assume at the edge of the chip 1 but is, in fact, much closer to the tip of the fibre 3. Also, a smooth radius can be seen between the two suspension points, i.e. between the contact point with the block 6 and the contact point with the chip 1. The deflection length L is thus calculated as: L = LV - (I tan 0) Equation I where L, = (distance between block 6 and chip 1) + (length of the V-groove to the tip of the fibre).
Linear elastic bending theory can provide a good estimation of the bending moment of the fibre. The theory for deflection of beams is derived from the general bending formula:
M E -=-=- Equation 2 I y R where: M is the pure bending moment (Nm) I is the second moment of area which, for a fibre with a circular cross-
section, is given by the equation I = 4, where d is the fibre diameter.
His the maximum stress, tensile or compressive, at a distance y from the beam neutral axis (for a fibrey = radius of the fibre, e.g. 62.5pm.
E is the elastic (Youngs) modulus of the fibre material (Nm2).
R is the radius of curvature (m) to the neutral axis.
The deflection of the fibre is analogous to the deflection of a cantilever (see Figure 1 B) with a concentrated end load which provides the relationship: M 3YEI Eq. 3 Where W = length of fibre and Y - its actual deflection Figure 1 C shows how the parameters of Figures 1A and 1 B relate to each other.
By trigonometry: W =- and Y = P Eq. 4 & 5 cos cos Substituting equations 4 & 5 into equation 3 gives 3dpEI CoS2 3dpEI cosR LicosR L2 Eq. 6 3YEI 3dpEI costs thus M W2 = L2 (From Eq. 3 and Eq. 6)
! From Eq. 1: tang = [v Eq.7 Combining equations 2 and gives L2 _ 3dpEycosP Eq. 8 or thus L2 3EYcos0(Lv - L) Eq. 8 substituting Eq. 7 Rearranging gives: = 3Ey(Lv - L)cos2 Eq. 9 Equation 9 thus gives a relationship between the distance L, the angle and the maximum tensile stress of the fibre.
From the above it can be seen that in order to impart the desired level of strain on the fibre the distance L and the angle must be accurately controlled. Rather than specifying the maximum tensile stress permitted within the fibre, it is often easier to specify a minimum bend radius for the fibre. Typically, if the bend radius is less than 4.5mm, the fibre fractures. In the arrangement described the bend radius is preferably at least 1 5-20mm and, most preferably, even greater, e.g. around 28mm.
Based on this analysis, a new form of attachment block 10 is proposed as shown in Figure 2. This comprises a first angled portion 11 fabricated at the
angle to the horizontal for supporting a stripped fibre and a second angled portion 12 which is fabricated at an angle to the horizontal for supporting the fibre jacket tie-off. A first generally planar region 13 is provided between the front edge 10A of the block and the first angled portion 11 and a second generally planar region 14 is provided between the first and second angled portions 11 and 12. Alternatively, the second generally planar region 14 may be omitted so the first and second angled portion 11 and 12 meet at step 14A.
The first generally planar region 13 is critical in determining the distance L as the block is designed to butt up against the edge of the optical chip as shown in Figure 3. The second generally planar region 14 (if provided) also provides a pre-determined spacing between the first and second inclined portions 11 and 12.
A step 13A is preferably provided between the first angled portion 11 and the first generally planar region 13 so the region 13 is at a lower level to the front edge of portion 11 to provide additional clearance beneath the elastically deformed part of the fibre 3.
The modified block 10 has a large planar underside which is mounted on the same base 2 as the chip 1 and thus reduces variations in the angle which can arise when a much smaller block 6 such as that disclosed in US6075914 is used. The bond between the underside of the block 10 and base 2 and that between the underside of the chip 1 and the base 2 are also more likely to be of uniform thickness due to the fact that they are both fabricated between relatively large planar surfaces.
The angle of the second inclined portion 12 supports the fibre 3 at an angle as it enters the package so the bend allowing the fibre to be supported on the first inclined portion is more gradual. As the second inclined region 12 is an integral part of the block 10, its location, relative to the first inclined region 11
and relative to the chip 1, is pre-set. Devices can thus be easily and repeatedly fabricated with the required dimensional accuracy by simply mounting the block 10 on the base 2 with the front face 10A of the block butted up against the edge of the chip 1.
The fabrication of these components as one unit also avoids the need for accurate alignment of different components on the base 2.
Furthermore, it will be seen that both the first and second inclined portions 11, 12 have planar upper surfaces. This is because lateral misalignment of the fibre 3, e.g. by one or two degrees, has little effect upon the coupling of the fibre 3 to the chip 1. In particular, the second inclined portion 12 is planar rather than channel-shaped as in US6075914 as this arrangement is more conducive to mass production. Rather than having to fabricate an accurately dimensioned channel-shaped support to ensure that the fibre is held in the desired location, it is simpler to provide a planar region and to rely on accurate placement machinery to locate the fibre 3 in the appropriate position on the surface 12.
In the fabrication of the arrangement described in US6075914, the fibre block 6 was usually secured to the fibre 3 before the block 6 was secured to the base 2 and adhesive was applied to the channel-shaped support first and the fibre 3 then secured thereto. With the arrangement described herein, the block 10 is first secured to the base 2. A fibre 3 is then located and held in the correct position on the block 10 and, finally, adhesive applied over the fibre 3 to secure it to the first and second inclined regions 1 1 and 12.
Figure 4 shows a perspective view of a complete package 15 incorporating an optical chip 1 and an optical fibre 3 mounted thereon via a block 10 as described above.
The block 10 should be made of a material which can be manufactured, e.g. by sintering, moulding etc. to a high degree of accuracy. Suitable materials include a machinable glass ceramic, such as MACOR (trade name) produced by Corning, or a plastics material, e.g. a polymer.
Claims (12)
1. Apparatus for connecting an optical fibre to an optical device, the apparatus comprising: a generally planar optical substrate mounted on a generally planar base member, the optical substrate having locating means thereon for locating the end of an optical fibre relative to an optical device on the substrate; and a fibre support member for supporting the fibre in a desired location relative to the substrate, the fibre support member being mounted on the base and comprising a first support surface inclined to the plane of the base for supporting a stripped portion of the fibre at an angle to the plane of the substrate so the fibre is held in a state of elastic deformation to assist in holding the fibre in contact with the locating means (without the fibre being secured thereto), the dimensions of the support member and the angle being selected so that, when the support member is located in contact with said edge of the substrate and a fibre secured to the first support surface, the elastic deformation of the fibre is automatically determined thereby and arranged to be below a pre-set magnitude.
2. Apparatus as claimed in claim 1 arranged such that the minimum bend radius of the fibre is at least 15-20mm, and preferably greater than 28mm.
3. Apparatus as claimed in claim 1 or 2 in which the dimensions of the support member and the angle are selected so as to satisfy the following relationship: 3Ey(Lv -L)cos = L2 sin where E is the elastic modulus of the fibre material y is the radius of the fibre
L and Lv are is the distances along the plane of the base from the end of the fibre and its point of contact with the support member nearest the end of the fibre, in an undeformed and deformed state, respectively.
4. Apparatus as claimed in claim 3 in which, for a silicon fibre having a diameter of about 125 microns, the angle lies in the range 2.5 to 3.5 degrees and the distance L lies in the range 2.1 to 2.5mm.
5. Apparatus as claimed in any preceding claim in which the support member has a second support surface for supporting an unstripped portion of the fibre.
6. Apparatus as claimed in claim 5 in which the second support surface is inclined at an angle to the plane of the base member so as to reduce the required degree of deformation of the fibre between the first and second support surfaces.
7. Apparatus as claimed in claim 5 or 6 in which the second support surface is substantially planar.
8. Apparatus as claimed in any preceding claim in which said locating means comprises a V-groove formed within the substrate.
9. Apparatus as claimed in any preceding claim in which the support member is formed of a machinable glass ceramic or a plastics material.
10. Apparatus for connecting an optical fibre to an optical device substantially as hereinbefore described with reference to and/or as shown in one or more of Figures 2 - of the accompanying drawings.
11.According to a second aspect of the invention, there is provided a method of connecting an optical fibre to an optical device including the following steps: forming locating means on a generally planar optical substrate for locating the end of an optical fibre relative to an optical device on the substrate; mounting the optical substrate on a generally planar base member; forming a fibre support member comprising a first support surface for supporting a stripped portion of the fibre; mounting the fibre support member on the base member in contact with an edge of the substrate; locating a fibre in a desired position on the optical substrate and the support member; and securing the fibre to the support member, the first support surface being inclined at an angle Bto the plane of the base member so the fibre is held in a state of elastic deformation to assist in holding the fibre in contact with the locating means on the substrate without the fibre being secured thereto, the angle and the dimensions of the support member being selected so that, mounting of the support member in contact with said edge of the substrate automatically determines the elastic deformation of the fibre whereby this is arranged to be below a pre-set magnitude.
12. A method of connecting an optical fibre to an optical device substantially as hereinbefore described with reference to one or more of Figures 2 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0210053A GB2388204A (en) | 2002-05-02 | 2002-05-02 | Connecting optic fibre in elastic deformation to optical device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0210053A GB2388204A (en) | 2002-05-02 | 2002-05-02 | Connecting optic fibre in elastic deformation to optical device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0210053D0 GB0210053D0 (en) | 2002-06-12 |
| GB2388204A true GB2388204A (en) | 2003-11-05 |
Family
ID=9935938
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0210053A Withdrawn GB2388204A (en) | 2002-05-02 | 2002-05-02 | Connecting optic fibre in elastic deformation to optical device |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2388204A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2330424A (en) * | 1997-11-21 | 1999-04-21 | Bookham Technology Ltd | Apparatus for connecting an optical fibre to an optical device |
| GB2340620A (en) * | 1998-08-12 | 2000-02-23 | Bookham Technology Ltd | Making an optic fibre integrated optic device package` |
-
2002
- 2002-05-02 GB GB0210053A patent/GB2388204A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2330424A (en) * | 1997-11-21 | 1999-04-21 | Bookham Technology Ltd | Apparatus for connecting an optical fibre to an optical device |
| GB2340620A (en) * | 1998-08-12 | 2000-02-23 | Bookham Technology Ltd | Making an optic fibre integrated optic device package` |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0210053D0 (en) | 2002-06-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |