GB2369197A - Manufacturing long period fibre gratings by using reflecting bodies - Google Patents
Manufacturing long period fibre gratings by using reflecting bodies Download PDFInfo
- Publication number
- GB2369197A GB2369197A GB0203825A GB0203825A GB2369197A GB 2369197 A GB2369197 A GB 2369197A GB 0203825 A GB0203825 A GB 0203825A GB 0203825 A GB0203825 A GB 0203825A GB 2369197 A GB2369197 A GB 2369197A
- Authority
- GB
- United Kingdom
- Prior art keywords
- optical fiber
- long period
- fiber
- laser source
- gratings
- 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.)
- Granted
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
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
- G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
- G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
- G02B6/02152—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating involving moving the fibre or a manufacturing element, stretching of the fibre
-
- 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
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
- G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
- G02B6/0208—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response
- G02B6/021—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response characterised by the core or cladding or coating, e.g. materials, radial refractive index profiles, cladding shape
- G02B6/02109—Refractive index modulation gratings, e.g. Bragg gratings characterised by their structure, wavelength response characterised by the core or cladding or coating, e.g. materials, radial refractive index profiles, cladding shape having polarization sensitive features, e.g. reduced photo-induced birefringence
-
- 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
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
- G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
- G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
- G02B6/02142—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating based on illuminating or irradiating an amplitude mask, i.e. a mask having a repetitive intensity modulating pattern
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
Abstract
Apparatus for manufacturing long period fibre gratings has an ultraviolet (UV) laser source 800. An amplitude mask 804 is disposed over an optic fibre 812, for transmitting light emitted from the ultraviolet laser source 800 to the optic fibre 812 at periodic distant intervals. Reflecting bodies 814 are installed on the opposite side of the optic fibre 812 to the amplitude mask 804, for reflecting light which has passed through the optic fibre 812. Also disclosed is rotation of the optic fibre at one or both ends (figures 4 and 7).
Description
APPARATUS FOR MANUFACTURING LONG-PERIOD FIBER GRATINGS WITH LOW DEPENDENCE ON POLARIZATION AND LONG PERIOD FIBER GRATINGS MANUFACTURED BY THE
SAME
BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an apparatus for manufacturing long period fiber gratings with low polarization dependence, and long period fiber gratings manufactured by the same.
2. Description of the Related Art
It is known that an induction of perturbations in the refractive index of an optical fiber core using ultraviolet (UV) laser induces birefringence within an optical fiber due to anisotropic perturbations in the refractive index from the viewpoint of the cross-section of the core. In 1994, A. M. Vengsarkar analyzed that birefringence is due to geometrical asymmetry in respect of the manufacturing conditions for irradiating UV laser to the lateral side of an optical fiber. A. M. Vensarkar, Qian Zhong, Daryl Inniss, W. A. Reed, P. J. Lemaire, and S. G. Kosinski, 'Birefringence reduction in side-written photoinduced fiber devices by a dual-exposure method. 'Opt. Lett., Lett. ,vol.vol. 19, pp. 1260-1262,1994. FIG. 1 shows a perturbation in refractive index with respect to a light irradiation direction, when UV light is irradiated to one side of an optical fiber. Reference numeral 100 is an optical fiber, reference numeral 101 denotes the refractive index of a cladding, reference numeral 102 denotes the refractive index of a core, to which UV light is not
irradiated, and reference numeral 103 denotes the refractive index of the core when UV light is irradiated thereto. As shown in FIG. 1, it can be seen that the refractive index of a core is perturbed according to the direction of irradiation of UV light.
Fiber gratings, which are fabricated by perturbations in the refractive index of an optical fiber core due to the irradiation of UV light, also use an asymmetrical irradiation method according to manufacture circumstances.
Thus, polarization dependency is generated. In particular, the polarization dependency becomes serious in the case of long period fiber gratings which require a refractive index perturbation which is about ten times greater than that for fiber bragg gratings or short period fiber gratings. This characteristic causes a change in insertion loss due to the polarization of a device, that is, a polarization dependent loss (PDL) or polarization mode dispersion (PMD), so that long period fiber gratings may not be suitable for optical communication elements. In other words, irradiation of UV light onto only one side of an optical fiber induces a birefringence phenomenon in which the optical fiber has different refractive indices along its axis, so that long period fiber gratings have polarization dependency.
FIG. 2 is a graph showing PDL response characteristics with respect to the wavelengths of conventional long period fiber gratings, and FIG. 3 is a graph showing a variation in PDL with respect to the loss peaks of conventional long period fiber gratings. As shown in FIGS. 2 and 3, upon optical transmission, the PDL of long period fiber gratings increases as a loss peak increases. Therefore, a long period fiber grating with a large loss peak has a significantly large PDL. In order to reduce the large PDL, a reduction in the polarization dependence of long period fiber gratings is required.
SUMMARY OF THE INVENTION
According to the invention in a first aspect there is provided an apparatus for manufacturing long period fiber gratings, the apparatus including: an ultraviolet laser source; an amplitude mask disposed over an optical fiber, for transmitting light emitted from the ultraviolet laser source to the optical fiber at periodic distance intervals; and reflecting bodies installed on the opposite of the optical fiber to the amplitude mask, for reflecting light which has passed through the optical fiber.
According to the invention in a second aspect there is provided an apparatus for manufacturing optical fiber gratings, the apparatus including: an optical fiber, one end of which has been rotated at least once with respect to the other end; an ultraviolet laser source; and an amplitude mask disposed over the optical fiber, for transmitting light emitted from the ultraviolet laser source at periodic distance intervals.
According to the invention in a third aspect there is provided an apparatus for manufacturing fiber gratings, the apparatus including: an optical fiber holder for rotating both ends of an optical fiber at the same speed while supporting both ends of the optical fiber; an ultraviolet laser source; and an amplitude mask disposed over the optical fiber which is being rotated by the optical fiber holder, for transmitting ultraviolet laser light emitted from the ultraviolet laser source to the optical fiber at periodic distance intervals.
According to a fourth aspect of the invention there is provided a long period fiber grating manufactured by a method including: twisting an optical fiber at least once; irradiating light to the twisted optical fiber at periodic distance intervals; and untwisting the twisted optical fiber.
According to a fifth aspect of the invention there is provided a long period fiber grating manufactured by a method including : rotating both ends of an optical fiber at the same speed; and irradiating light to the optical fiber which is rotating, at periodic distance intervals.
An advantage of the first aspect of the invention is to provide an apparatus for manufacturing long period fiber gratings with low polarization dependence, in which UV light is irradiated to an optical fiber, both ends of which are fixed, and UV light which has passed through the optical fiber is axially reflected to be re-irradiated to the optical fiber.
An advantage of the second aspect of the invention is to provide an apparatus for manufacturing long period fiber gratings with low polarization dependence, in which ultraviolet (UV) light is irradiated after one end of an optical fiber is rotated at least once with respect to the other end thereof.
An advantage of the third aspect of the invention is to provide an apparatus for manufacturing long period fiber gratings with low polarization dependence, in which UV light is irradiated to an optical fiber, both ends of which are rotated at the same speed.
An advantage of the fourth and fifth aspects of the invention is to provide a long period fiber grating with low polarization dependence, which is manufactured by the manufacturing apparatus.
There now follows a description of preferred embodiments of the invention, by way of non-limiting example, with reference to the attached drawings in which:
FIG. 1 is a graph showing a refractive index perturbation with respect to a direction of light irradiation when ultraviolet (UV) light is
irradiated to only one side of an optical fiber ; FIG. 2 is a graph showing polarization dependent loss (PDL) characteristics with respect to the wavelengths of conventional long period fiber gratings;
FIG. 3 is a graph showing a variation in PDL with respect to the loss peaks of conventional long period fiber gratings;
FIG. 4 is a block diagram illustrating the configuration of an apparatus for manufacturing long period fiber gratings, according to an embodiment of the present invention;
FIG. 5 is a conceptual view illustrating a variation in refractive index when a twisted optical fiber is untwisted after a grating is fabricated on the twisted optical fiber;
FIGS. 6A and 6B are graphs showing the results of an experiment performed with respect to a conventional long period fiber grating and a long period fiber grating according to the present invention;
FIG. 7 is a block diagram illustrating the configuration of an apparatus for manufacturing long period fiber gratings, according to another embodiment of the present invention; and
FIG. 8 is a block diagram illustrating the configuration of an apparatus for manufacturing long period fiber gratings, according to still another embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 4, an apparatus for manufacturing long period fiber gratings according to an embodiment of the present invention includes a UV laser source 400, a lense 402, an amplitude mask 404, an optical fiber holder 408 and an optical fiber 406 twisted by the optical fiber holder 408.
Preferably, one end of the optical fiber holder 408 fixes one end of the optical fiber 406, and the other end thereof is rotatable so that the other end
of the optical fiber 406 can be twisted. In the manufacture of long period fiber gratings, first, the optical fiber holder 408 fixes one end of the optical fiber 406 and rotates the other end thereof, thereby twisting the optical fiber 406. It is preferable that the entire optical fiber 406 is evenly twisted 360 .
The lense 402 focuses UV light emitted from the UV laser source 400. The amplitude mask 404 has light transmission regions at periodic distance intervals, and is disposed above the optical fiber 406. Thus, the amplitude mask 404 transmits light which has been focused by the lense 402 through the light transmission regions. The transmitted light is irradiated to the twisted optical fiber 406. The irradiated light perturbs the refractive index of the core of the optical fiber 406 according to the period (A) of the amplitude mask 404, resulting in a grating. At this time, birefringence is induced within the optical fiber due to the refractive index perturbations of the optical fiber core. The induced birefringence perturbs the valid refractive index nco of the core and the coupling constant K of the core as shown in the following Equation 1 :
n c =sin' (1) el
wherein 4 denotes the peak wavelength of a long period fiber grating, A denotes the period of a long period fiber grating, nco denotes the valid refractive index of a core, n denotes the valid refractive index of an n-th cl cladding mode, p denotes a coupling ratio of power to the n-th cladding cl mode at a peak wavelength, K denotes a coupling constant, and L denotes the length of a grating, so that the spectrum of a long period fiber grating varies with the polarization of incident light.
Thus, it is required to make the optical fiber 406 immune to polarization. To do this, in the present invention, one end of the optical fiber 406 is fixed, and the other end thereof is rotated at least once so that the optical fiber is twisted 360 , as described above. When one end of an optical fiber is rotated as described above, it is important to solidly fix the optical fiber to prevent slipping within the optical fiber holder 408. Once an optical fiber is twisted, a grating is fabricated on the twisted optical fiber, the twisted optical fiber is then untwisted, and spiral perturbation in refractive index appears in the core. Thus, the grating becomes independent upon the particular polarization state of light. FIG. 5 conceptually illustrates spiral perturbation in refractive index when a twisted optical fiber is untwisted after a grating is fabricated on the twisted optical fiber.
As shown in FIG. 5, it can be seen that spiral perturbation in the refractive index on the cross-section of the core of the optical fiber 406 with respect to the total length appears isotropical.
FIGS. 6A and 6B show the results of an experiment performed with respect to a conventional long period fiber grating and a long period fiber grating according to the present invention. FIG. 6A shows the results of measurement of PDL with respect to the wavelength. It can be seen from
FIG. 6A that the PDL in the present invention is significantly reduced compared to the PDL in the prior art within a measured wavelength range.
FIG. 6B shows the results of measurement of PDL with respect to a loss peak. In FIG. 6B, the PDL in the prior art at a loss peak of 22. 1dB is 1. 83dB, and the PDL in the present invention at a loss peak of 24. 5dB is 0.79dB, so that it can be seen that the PDL was reduced by IdB or more. It becomes evident that the PDL in the present invention generally decreases
by at least 60% of the PDL in the prior art, and that the difference in the PDL between the present invention and the prior art increases as the loss peak increases.
FIG. 7 is a block diagram illustrating the configuration of an apparatus for manufacturing long period fiber gratings, according to another embodiment of the present invention. The apparatus of FIG. 7 includes a UV laser source 700, a lense 702, an amplitude mask 704, an optical fiber 710 and an optical fiber holder 712.
The operations of the UV laser source 700, the lense 702 and the amplitude mask 704 are the same as those of the counterparts of FIG. 4, except that both ends of the optical fiber holder 712 for supporting both ends of the optical fiber 710 can rotate at the same speed, and thus the optical fiber 710 can rotate at a constant speed. That is, the optical fiber 710 is rotated by rotation of the optical fiber holder 712, and UV laser which has passed through the amplitude mask 704 is irradiated upon the optical fiber 710 which is being rotated, so that the refractive profile of the core of the optical fiber 710 is isotropic in the direction perpendicular to the axis of the core, that is, in a cross-section of the core of the optical fiber 710.
FIG. 8 is a block diagram illustrating the configuration of an apparatus for manufacturing long period fiber gratings, according to still another embodiment of the present invention. The apparatus of FIG. 8 includes a
UV laser source 800, a lense 802, an amplitude mask 804, an optical fiber 812 and reflecting bodies 814. The reflecting bodies 814 are on the opposite side of the optical fiber 812 to the amplitude mask 804.
The operations of the UV laser source 800, the lense 802 and the amplitude mask 804 are the same as those of the counterparts of FIG. 4, except that
when light which has passed through the amplitude mask 804 is irradiated upon the optical fiber 812, light which has passed through the optical fiber 812 is reflected by the reflecting bodies 814 and re-irradiated upon the optical fiber, such that the refractive index of the core of the optical fiber 812 changes isotropically from the viewpoint of the cross-section of the core of the optical fiber 812.
According to the present invention, in the manufacture of long period fiber gratings, the refractive index of an optical fiber core is perturbed by irradiating UV light to a twisted optical fiber or by irradiating UV light to an optical fiber while rotating the optical fiber, so that the refractive index profile of the core of the optical fiber averages out to be isotopic over the length of the grating. Therefore, a long period fiber grating which is less sensitive to polarization than that in the prior art can be obtained.
Claims (8)
1. An apparatus for manufacturing long period fiber gratings, comprising : an ultraviolet laser source; an amplitude mask disposed over an optical fiber, for transmitting light emitted from the ultraviolet laser source to the optical fiber at periodic distance intervals; and reflecting bodies installed on the opposite of the optical fiber to the amplitude mask, for reflecting light which has passed through the optical fiber.
2. An apparatus for manufacturing long period fiber gratings, comprising : an optical fiber, one end of which has been rotated at least once with respect to the other end; an ultraviolet laser source; and an amplitude mask disposed over the optical fiber, for transmitting light emitted from the ultraviolet laser source at periodic distance intervals.
3. The apparatus of claim 2, wherein the optical fiber further comprises an optical fiber holder for fixing one end of the optical fiber and rotating the other end of the optical fiber at least once with respect to the fixed end of the optical fiber while supporting the rotated end of the optical fiber.
4. An apparatus for manufacturing long period fiber gratings, comprising: an optical fiber holder for rotating both ends of an optical fiber at the same speed while supporting both ends of the optical fiber; an ultraviolet laser source; and
an amplitude mask disposed over the optical fiber which is being rotated by the optical fiber holder, for transmitting ultraviolet laser light emitted from the ultraviolet laser source to the optical fiber at periodic distance intervals.
5. A long period fiber grating manufactured by a method comprising: twisting an optical fiber at least once; irradiating light to the twisted optical fiber at periodic distance intervals; and untwisting the twisted optical fiber.
6. A long period fiber grating manufactured by a method comprising: rotating both ends of an optical fiber at the same speed; and irradiating light to the optical fiber which is rotating, at periodic distance intervals.
7. An apparatus generally as herein described, with reference to and/or as illustrated in Figure 4,7 and 8 of the accompanying drawings.
8. A long period fiber grating generally as herein described, with reference to and/or as illustrated in Figures 1,5 and 6 of the accompanying drawings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1019990030833A KR100303284B1 (en) | 1999-07-28 | 1999-07-28 | Apparatus for manufacturing long period optical fiber gratings having less dependence on polarization and long period optical fiber gratings manufactured by the same |
| GB0017855A GB2352531B (en) | 1999-07-28 | 2000-07-21 | A method of manufacturing long period fibre gratings |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB0203825D0 GB0203825D0 (en) | 2002-04-03 |
| GB2369197A true GB2369197A (en) | 2002-05-22 |
| GB2369197B GB2369197B (en) | 2003-04-16 |
Family
ID=26244690
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0203825A Expired - Fee Related GB2369197B (en) | 1999-07-28 | 2000-07-21 | Manufacturing long fiber gratings by using reflecting bodies |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2369197B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999045417A1 (en) * | 1998-03-02 | 1999-09-10 | Uniphase Fibre Components Pty. Limited | Grating writing method and apparatus |
| WO2000008500A1 (en) * | 1998-08-03 | 2000-02-17 | British Telecommunications Public Limited Company | Apparatus and method for generating an interference pattern to be written as a grating in a sample of a photosensitive material |
-
2000
- 2000-07-21 GB GB0203825A patent/GB2369197B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999045417A1 (en) * | 1998-03-02 | 1999-09-10 | Uniphase Fibre Components Pty. Limited | Grating writing method and apparatus |
| WO2000008500A1 (en) * | 1998-08-03 | 2000-02-17 | British Telecommunications Public Limited Company | Apparatus and method for generating an interference pattern to be written as a grating in a sample of a photosensitive material |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0203825D0 (en) | 2002-04-03 |
| GB2369197B (en) | 2003-04-16 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| GB2352531A (en) | Apparatus for manufacturing fibre optic gratings by rotating optic fibre | |
| US6925230B2 (en) | Long period chiral fiber grating apparatus | |
| US5859944A (en) | Optical connector | |
| Yang et al. | Twist sensor based on long period grating and tilted Bragg grating written in few-mode fibers | |
| KR100342532B1 (en) | Fabrication device of polarization insensitive long period fiber grating | |
| AU728818B2 (en) | Optical dispersion compensation | |
| CA2190668C (en) | Optical connector | |
| Konnov et al. | Inscription and visualization of tilted fiber Bragg gratings | |
| Estudillo-Ayala et al. | Long period fiber grating produced by arc discharges | |
| US7269316B2 (en) | Method for restoring photosensitivity in hydrogen or deuterium loaded large diameter optical waveguide | |
| Reyes et al. | Tunable PDL of twisted-tilted fiber gratings | |
| GB2369197A (en) | Manufacturing long period fibre gratings by using reflecting bodies | |
| Ramachandran et al. | High extinction, broadband polarisers using long-period fibre gratings in few-mode fibres | |
| US6766080B2 (en) | Optical waveguide type defraction grating device and a method of manufacturing thereof | |
| US6707966B1 (en) | Twisted long-period fiber grating and method for reducing polarization dependent loss and shifting wavelength of a long-perion fiber grating | |
| Caucheteur et al. | Transverse force sensor exploiting the birefringence effect in uniform fibre Bragg gratings | |
| Grüner-Nielsen et al. | Direct measurement of polarization dependency of mode conversion in a long period grating | |
| Yamasaki | Characteristics of long period fiber grating utilizing periodic stress relaxation under high temperature environment | |
| US7024075B2 (en) | Reducing insertion losses of a written in grating with mode coupling in the cladding | |
| Holmes et al. | Development of radiation-mode filters for WDM | |
| JP2001356221A (en) | Compensation of polarization mode dispersion of grating written in optical fiber | |
| Jiang et al. | Twist Sensor Using Chiral Long-Period Grating Written in the Double-Cladding Fiber | |
| JPH10288715A (en) | Two-wavelength stop type optical fiber grating | |
| Guan et al. | A novel long-period fiber grating torsion sensor | |
| Okude et al. | A novel technique for suppressing undesired coupling of LP01 mode to cladding modes in fiber Bragg gratings |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20070721 |