U.S. patent application number 09/748429 was filed with the patent office on 2001-08-23 for apparatus and method for fabricating multi-period optical fiber grating.
This patent application is currently assigned to SAMSUNG ELECTRONIC CO., LTD.. Invention is credited to Kim, Min-Sung, Shin, Sang-Gil.
Application Number | 20010016099 09/748429 |
Document ID | / |
Family ID | 19631436 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010016099 |
Kind Code |
A1 |
Shin, Sang-Gil ; et
al. |
August 23, 2001 |
Apparatus and method for fabricating multi-period optical fiber
grating
Abstract
Disclosed is an apparatus and method for fabricating a
multi-period optical fiber grating. The apparatus includes an
optical light source; a movable optical fiber having a first part
of the optical fiber and at least a second part of the optical
fiber bent from the first part of the optical fiber and arranged
substantially parallel with the first part of the optical fiber;
and a multi-period amplitude mask including a first sector having a
predetermined on-off ratio corresponding to the first part of the
optical fiber and at least a second sector disposed substantially
parallel with the first sector and having an on-off ratio different
from the predetermined on-off ratio, wherein the mask position on
top of the fiber is translated in relation to the light source so
that the gratings of differing periods can be formed along the
exposed optical fiber member.
Inventors: |
Shin, Sang-Gil; (Yongin-shi,
KR) ; Kim, Min-Sung; (Songnam-shi, KR) |
Correspondence
Address: |
KLAUBER & JACKSON
411 HACKENSACK AVENUE
HACKENSACK
NJ
07601
|
Assignee: |
SAMSUNG ELECTRONIC CO.,
LTD.
|
Family ID: |
19631436 |
Appl. No.: |
09/748429 |
Filed: |
December 26, 2000 |
Current U.S.
Class: |
385/37 ;
430/290 |
Current CPC
Class: |
G02B 6/02152 20130101;
G02B 6/02142 20130101 |
Class at
Publication: |
385/37 ;
430/290 |
International
Class: |
G02B 006/34 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 1999 |
KR |
P1999-64119 |
Claims
What is claimed is:
1. An apparatus for fabricating a multi-period optical fiber
grating, comprising: means for generating an optical light beam; a
continuous optical fiber member having a first part and at least a
second part, said second portion bent around so that said first
part is in a substantially parallel relationship with said second
part of said optical fiber; and, a multi-period amplitude mask
disposed between said light generating means and said optical
fiber, said mask having a first sector with a first series of
troughs defining a first predetermined on-off ratio responsive to
said first part of said fiber member and at least a second sector
with a second series of troughs defining a second predetermined
on-off ratio responsive to said second part of said fiber
member.
2. The apparatus of claim 1, wherein said first and second sectors
of said mask are arranged substantially parallel with each
other.
3. The apparatus of claim 1, wherein said first and second sectors
of said mask are integrally formed.
4. The apparatus of claim 1, wherein said mask position on top of
said optical fiber member is translated with respect to said
optical light source for allowing the light beam of said optical
light source through said respective section of said mask to the
grating of differing periods.
5. The apparatus of claim 1, further comprising a lens device
disposed between said light generating means and said mask for
enhancing the light effect of said light generating means.
6. A method for fabricating an optical fiber grating using a
device, which includes a fixed optical light source; a continuous
optical fiber having a first part and at least a second part bent
portion being substantially parallel with said first part; and a
multi-period amplitude mask having a first sector having a first
on-off ratio corresponding to said first part of said optical fiber
and at least a second sector in a parallel relationship with said
first sector having a second on-off ratio, the method comprising
the steps of: providing said first sector of said mask positioned
on the top of said first part of said optical fiber under said
optical light source; introducing light beams emitted from said
optical light source through said first sector of said mask to form
grating patterns of a first period on said first part of said
optical fiber by passing; moving said mask and said optical fiber
so that said second sector of said mask positioned on the top of
said second part of said optical fiber is located under said
optical light source; and, introducing light beams emitted from
said optical light source through said second sector of said mask
to form grating patterns of a second period on said second part of
said optical fiber.
Description
CLAIM OF PRIORITY
[0001] This application makes reference to and claims all benefits
accruing under 35 U.S.C. Section 119 from an application entitled,
"Apparatus and Method for Fabricating Multi-Period Optical Fiber
Grating", filed with the Korean Industrial Property Office on Dec.
28, 1999 and there duly assigned Ser. No. 99-64119.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to a long-period
optical fiber grating used as a gain equalized filter, and more
particularly, to an apparatus and method for fabricating gratings
of different periods.
[0004] 2. Description of the Related Art
[0005] Fiber gratings are periodic variations in a refractive index
along the length of a fiber. It is possible to make fibers in which
the refractive index varies regularly along their length. These
fibers are called fiber gratings as they interact with light, and
their effects on light passing through them depend very strongly on
the wavelength.
[0006] In general, an optical fiber grating is a row of fine
parallel lines, usually on a reflective surface. Light waves bounce
off the lines at an angle that depends on their wavelength. Thus,
the fiber grating is used as a filter for selecting a predetermined
wavelength directed to the particular core of an optical fiber as
well as eliminating or reflecting light at a particular wavelength
by periodically inducing the variance of a refractive index of the
optical fiber through the provision of ultraviolet light.
Ultraviolet light creates fiber gratings by breaking atomic bonds
in the fiber member. Typically, the optical fiber grating is
classified into a short-period optical fiber grating and a
long-period optical fiber grating depending on its period of
time.
[0007] A short-period optical fiber grating reflects a specific
wavelength for performing a filtering function. In contrast,
long-period grating (LPG) devices selectively remove light at
specific wavelengths by coupling light from one optical mode of a
fiber to another mode propagating in the same direction, with very
low back-reflection. In particular, the long-period grating is
utilized to couple light from a core mode to a cladding mode in the
range from tens of kilometers to hundreds of kilometers, during
which light at specific wavelengths can be removed. In essence, the
long-period grating devices serve as a gain equalized filter in an
erbium-doped optical fiber amplifier.
[0008] When the long-period grating is utilized as a gain equalized
filter, there are some instances where the long-period grating
requires multi-period gratings. FIG. 1 is a simplified diagram
illustrating an optical fiber F with different long-period grating
patterns according to the conventional art. Referring to FIG. 1,
the long-period grating patterns, g1, g2 and g3, exhibiting
gratings of differing periods are disposed along the optical fiber
F in the direction of one axis. In this case, the notation, F1, F2
and F3 along the optical fiber represent the respective long-period
grating patterns that are interconnected for use as a gain
equalized filter.
[0009] The prior art system has some drawbacks as the gain
equalizing long-period grating patterns have to be interconnected
using a fusion splicer (or other similar alternatives). Moreover,
the gain equalizing long-period grating patterns require an
additional means, such as a contraction tube to secure the
connection as the connected regions are easy to break. Furthermore,
concise accuracy and costly high-tech equipment are required for
the above interconnection process.
SUMMARY OF THE INVENTION
[0010] It is, therefore, an object of the present invention to
provide an apparatus and method for fabricating a multi-period
grating device using a multi-period amplitude mask with a plurality
of on-off ratios.
[0011] It is another object of the present invention to provide an
apparatus and method for fabricating a multi-period grating device
with gratings of differing periods formed on a single optical fiber
using a multi-period amplitude mask.
[0012] It is still another object of the present invention to
provide an apparatus and method for fabricating a multi-period
grating device in an economical way.
[0013] To achieve the above objects, there is provided an apparatus
for fabricating a multi-period optical fiber grating, which
includes: an optical source; an optical fiber having a first part
of the optical fiber and at least one second part of the optical
fiber continuously connected to the first part and arranged
substantially in a parallel relationship with the first part of the
optical fiber; and a multi-period amplitude mask disposed between
the optical source and the optical fiber, wherein the multi-period
mask comprising the first section with a first on-off ratio
corresponding to the first part of the optical fiber and at least
one second section being substantially parallel with the first
sector with a second on-off ratio, and wherein gratings of
differing periods can be fabricated by passing a light beam through
the periodic first and second sections of the mask.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The above and other objects, features, and advantages of the
present invention will become more apparent from the following
detailed description when taken in conjunction with the
accompanying drawings, in which:
[0015] FIG. 1 is a view illustrating the method for fabricating a
gain equalized filter by interconnecting three long-period grating
patterns having different periods, respectively, according to an
embodiment of the conventional art;
[0016] FIG. 2 is a cross view illustrating a multi-period amplitude
mask having various on-off ratios according to a preferred
embodiment of the present invention;
[0017] FIG. 3a to FIG. 3c are top views illustrating the apparatus
and method for fabricating a long-period grating using a
multi-period amplitude mask according to a preferred embodiment of
the present invention; and,
[0018] FIG. 4 is a view illustrating the optical fiber having
grating patterns fabricated by using a multi-period amplitude mask
according to a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] A preferred embodiment of the present invention will be
described herein below with reference to the accompanying drawings.
For the purpose of clarity, well-known functions or constructions
are not described in detail as they would obscure the invention
with unnecessary detail.
[0020] FIG. 2 is a cross view illustrating the amplitude mask used
for fabricating an optical fiber grating according to the preferred
embodiment of the present invention. Referring to FIG. 2, the
amplitude mask according to the present invention is a multi- mask
device, which includes different shapes and spacing between
troughs. Multiple sets of a series of parallel apertures are used
to fabricate gratings of differing periods by introducing an
external ultraviolet light source through a different periodicity
of the amplitude mask 20. Here, the on-off ratio represents a ratio
of the refractive index of a core that is changed by the external
light source and the refractive index of the core that is not
affected by the light source.
[0021] The multi-period amplitude mask 20 shown in FIG. 2 contains
the first sector 210 having a first predetermined on-off ratio, the
second sector 220 having a second predetermined on-off ratio
greater than the first on-off ratio, and the third section 230
having a third predetermined on-off ratio greater than the second
on-off ratio. These different sectors 210, 220, and 230 are
integrally formed on a single amplitude mask. Here, the first,
second, and third sectors 210, 220 and 230 in the multi-period
amplitude mask 20 are arranged in a substantially parallel
relationship with each other along the arrow direction indicated by
number 2, and the parallel troughs in the respective on-off ratios
are arranged in a parallel along the direction indicated by number
1. It should be noted that the amplitude mask 20 according to the
present invention may include different patterns have various
on-off ratios and many sectors.
[0022] FIG. 3a to FIG. 3b are top views illustrating the method of
fabricating a multi-period grating using the multi-period amplitude
mask 20 according to the present invention. As shown in FIG.3, the
inventive apparatus includes an optical light source 30, an optical
fiber F where gratings of different periods are formed through the
provision of light beams emitted from the optical light source 30,
and a multi-period amplitude mask 20 with multiple rows of parallel
troughs for generating different patterns on the optical fiber F.
It is noted that any light source that is apparent to those in the
art for creating ultraviolet light beams may be incorporated in the
present invention. A cylindrical convex lens, which is not drawn in
FIG. 3a and FIG. 3b, may be optionally disposed between the optical
light source 30 and the multi-period amplitude mask 20 to maximize
the light efficiency. In the inventive invention of fabricating the
multi-period grating device, the optical light source 30 is located
in a fixed position and the multi-period amplitude mask 20 and the
optical fiber F are selectively translated in a spaced relation to
the optical light source 30.
[0023] With reference to FIGS. 3A and 3B, the optical fiber F is
bent around several times to form the first part F1, the second
part F2 and the third part F3, and the respective parts of the
optical fiber are aligned substantially parallel to each other. It
should be noted that the optical fiber F may be bent a few more
times in a similar manner depending on the number of on-off ratio
sections provided in the amplitude mask. Accordingly, the gain
equalizing long-period grating device with different periods can be
fabricated by passing a light beam through the inventive
multi-period amplitude mask 20.
[0024] Referring to FIG. 3a, an optical light source 30 is
positioned above one end of the optical fiber. The first sector 210
of the multi-period amplitude mask 20 is disposed between the
optical light source 30 and the optical fiber F. The first part F1
of the optical fiber is positioned below the first sector 210. To
be specific, the optical source 30, the first sector 210, and the
first part F1 of the optical fiber are positioned along the same
line. If the optical source 30 emits light beams, long-period
grating patterns with gratings of A1 period are formed in plurality
on the first part F1 of the optical fiber. As shown in FIG. 3b, the
multi-period amplitude mask 20 and the optical fiber F are slidably
movable in an arrow direction (indicated by number 3) through the
means of a carrier, which is not drawn in FIG. 3b.
[0025] In a similar fashion, the amplitude mask 20 and the second
part F2 of the optical fiber are moved so that the second sector
220 of the multi-period amplitude mask 20 is positioned below the
fixed optical light source 30. The optical light source 30, the
second sector 220, and the second part F2 of the optical fiber are
aligned along the same line so that the second part F2 of the
optical fiber can be exposed to the light emitted through the
second section 220 of the amplitude mask 20. If ultraviolet beams
are emitted by the optical source 30, optical fiber grating
patterns with gratings of A2 period are formed along the second
part F2 of the optical fiber.
[0026] Thereafter, as shown in FIG. 3c, the multi-period amplitude
mask 20 and the optical fiber F are moved in the direction
(indicated by an arrow 4) so that the third sector 230 of the
multi-period amplitude mask are positioned between the fixed
optical light source 30 and the third part F3 of the optical fiber
along the same line. Upon receiving the ultraviolet beams emitted
from the optical source 30, optical fiber grating patterns with
gratings of A3 period are formed on the third part F3 of the
optical fiber.
[0027] It should be noted that different extinction ratios and
bandwidths of the respective grating patterns can be adjusted by
varying the emitted amount of the ultraviolet beams and the lengths
of the grating patterns. Peak wavelengths of the grating patterns
also can be adjusted by varying the respective periods of the
amplitude mask.
[0028] FIG. 4 is a view illustrating different grating patterns
that are formed on an optical fiber by using the multi-period
amplitude mask according to the present invention. Referring to
FIG. 4, a grating pattern of g1 with A1 period is formed on the
first part F1 of the optical fiber, a grating of A2 period is
formed on the second part F2 of the optical fiber, and a grating of
A3 period is formed on the third part F3 of the optical fiber. By
providing the optical light source 20 in a fixed position while
moving the multi-period amplitude mask 20 and the optical fiber in
one direction at a predetermined velocity, a long-period optical
fiber grating having various on-off ratios can be formed
efficiently on a single optical fiber without splicing operation
and the costly equipment that is required in the prior art between
the respective parts of the optical fiber.
[0029] While the invention has been shown and described with
reference to a certain preferred embodiment thereof, it will be
understood by those skilled in the art that various changes in form
and detail may be made therein without departing from the spirit
and the scope of the invention as defined by the appended
claims.
* * * * *