JPH1093176A - Optical fiber amplifier and optical fiber type optical amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber amplifier and an optical fiber type amplifier which enable amplification of signal light with low excitation power and ease of incidence of the signal light. SOLUTION: An optical fiber of an optical fiber amplifier 120 is formed by a pumping light core 54 as a first core of a center portion, a second core 50 provided around the pumping light core 54 and having a refractive index lower than the pumping light core 54, and a cladding 52 provided around the second core 50 and having a refractive index lower than the second core 50. Pumping light 302 propagates within the pumping light core 54 and excites an optical amplifying section 56 as an optical amplification medium contained in the pumping light core 54. A signal light 300 is propagated through the second core 50 and is amplified by the excited optical amplifying section 56. Thus, the signal light 300 may be amplified with a low excitation power, and incidence of the signal light 300 may be facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical fiber amplifier using an organic optical fiber, an amplifier using the optical fiber amplifier, and an information communication path.

[0002]

2. Description of the Related Art As described in Japanese Patent Application Laid-Open No. 60-200208, a first core having the highest refractive index is provided at a central portion, and a second core having a low refractive index is provided around the first core.
In an optical fiber provided with a clad having the lowest refractive index around it, Nd is added to the first core, signal light is propagated to the first core, pump light is propagated to the second core, and the signal light is propagated. Amplifying optical fibers have been proposed.

Further, an optical amplifier using an organic optical fiber (hereinafter referred to as an organic optical fiber amplifier) is disclosed in Applied Optics, Vol. 34, pp. 988-992, 1
995 (Applied Optics, Vol. 3).
4, pp 988-992, 1995).

[0004]

However, in the above-mentioned optical amplifier using the conventional optical fiber, the first core is of a single mode, and high precision is required for the signal light to enter the first core. Adjustment was extremely difficult due to the need for alignment.

[0005] Organic optical fibers have a large core diameter.
Signal light can be easily incident on the core. Conventional organic optical fiber amplifiers are designed for organic optical fibers, and contain an amplifying dye in the entire core with a large diameter, requiring a very large optical power to excite the amplifying dye. there were.

Therefore, a continuous oscillation laser cannot be used for excitation, and a high-output pulse laser has been used.
In addition, because of excitation by pulsed light, a signal pulse having a repetition frequency higher than that of the excitation pulse cannot be amplified.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide an optical fiber amplifier which can amplify a signal light with a low pump power and can easily input the signal light. An object of the present invention is to provide an optical fiber type optical amplifier.

[0008]

In order to achieve the above object, the present invention provides an optical fiber amplifier for amplifying signal light similarly incident on an optical fiber by pumping light incident on the optical fiber. The fiber includes a first core at a central portion, a second core provided around the first core, and having a lower refractive index than the first core, and a fiber provided around the second core. The pumping light is formed of a clad having a lower refractive index than the second core, and the pumping light propagates in the first core to excite an optical amplification medium contained in the first core, and the signal light Is propagated in the second core and amplified by the excited optical amplification medium.

Another feature of the present invention resides in that the second core is formed so that the refractive index decreases from the center to the outer periphery.

Another feature of the present invention is that the second core focuses the signal light on the optical amplification medium.

Further, another feature of the present invention is that the first core and the second core are formed of an organic material having a light transmitting property.

Another feature of the present invention is that the optical amplification medium is an organic dye.

Further, another feature of the present invention is that an incident portion for receiving the pumping light and the signal light from the pumping light source, and an optical amplifying portion for amplifying the incident signal light also by the incident pumping light. The optical fiber according to claim 1, wherein the optical amplifying unit includes: an excitation unit that emits the pumping light and the amplified signal light. 8. Being an amplifier.

Further, another feature of the present invention is that the second core of the optical amplifying section that propagates the signal light has a core diameter larger than the diameter of the second core at the incident section or the output section. Is connected to a small optical fiber.

Another feature of the present invention is that an optical signal is transmitted using an optical amplification module for bidirectional communication for connecting an optical fiber having quartz as a core material and an optical fiber having an organic material as a core material. In the optical information communication path for transmission, the optical amplification module for bidirectional communication is an optical fiber type optical amplification device according to any one of claims 7 and 8.

Another feature of the present invention is an optical amplification method for amplifying a signal light by exciting an optical amplifying medium contained in an optical fiber with a pump light, wherein the pump is provided on a first core of the optical fiber. The signal light is propagated to the second core of the optical fiber while being propagated, and the signal light is amplified on the optical amplification medium by amplifying the signal light.

According to the present invention, the first core at the center of the optical fiber propagates the pumping light into the core, and excites the optical amplification medium arranged at regular intervals in the core by the pumping light.
The second core, which is provided around the first core and has a lower refractive index than the first core, propagates the signal light into the core and converts the signal light by the optical amplifying medium pumped in the first core. Amplify.
The second core is formed such that the refractive index decreases from the center toward the outer periphery, and focuses the signal light on the optical amplification medium. The cladding provided around the second core has a lower refractive index than the second core.

As described above, since the optical amplifying medium for amplifying the signal light is disposed in the first core having a small core diameter, the pump power may be small, and the signal light may be supplied to the second core having a large core diameter. Therefore, the incidence of signal light can be facilitated.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an optical fiber amplifier according to one embodiment of the present invention. As shown in FIG. 1, an optical fiber amplifier 120 includes a cladding 52 on the outer periphery, a core 50 as a second core for transmitting signal light, and a pumping core as a first core in the center. 54 are formed concentrically.

The core 50 and the excitation light core 54 are formed of an organic material having optical transparency, and an optical amplification section 56 containing an organic dye as an optical amplification medium is provided inside the excitation light core 54. It is formed at periodic intervals.

When the excitation light 302 is incident on the excitation light core 54, the excitation light 302 is confined in the excitation light core 54 and propagates. The organic dye that has received the excitation light 302 absorbs the excitation light 302 and enters an excited state. The signal light 300 is more angled than the pump light 302 and the optical fiber amplifier 120
Is condensed and incident on the incident side end face of. The signal light 300 propagates in the core 50.

Since the core 50 has a so-called graded index type refractive index distribution in which the refractive index decreases quadratically from the center to the outer periphery, the core 50 condenses light on the incident end face of the fiber. The incident signal light 300 is again focused like a signal light beam 304. In the present embodiment, an optical amplifier 56 is provided at this focal point.

In the optical amplifier 56, the signal light 300 is amplified by the excited organic dye. The signal light 300 is
While propagating through the core 50, it is attenuated by absorption and scattering by the medium of the core 50, but is amplified by the optical amplifying unit 56 beyond the attenuation.

In the present embodiment, light from an LED having a center at a wavelength of 590 nm is used as the signal light 300.
By modulating the current flowing through the ED, the intensity of the signal light is modulated.

The organic dye contained in the optical amplifier 56 must be selected according to the wavelength of the signal light 300. In the present example, the organic dye rhodamine B was contained in the optical amplifier 56 in accordance with the wavelength of the signal light 300 of 590 nm.

As the pumping light 302, a 532-nm light obtained by halving the wavelength of a 1064-nm fundamental wave of a continuously oscillating Nd-YAG laser by a non-linear crystal was used.
The organic dye absorbs the excitation light 302 to be in an excited state,
The signal light 300 is amplified by stimulated emission.

In addition to the present embodiment, a dye material may be selected in accordance with the wavelength of the signal light 30.
When a 650 nm semiconductor laser or LED is used as 0, DCM may be used as the organic dye, and when 850 nm, LSD821 may be used to excite with an argon ion laser or the like.

The effect of the present invention can be obtained by using a material used as a laser amplifying medium in the optical amplifying section 56 in addition to the organic dye as in this embodiment. Further, the material of the excitation light core 54 may be changed according to the amplification medium contained in the optical amplification section 56. For example, when Er is used as the amplification medium, glass may be used as the excitation light core 54.

In a conventional optical fiber amplifier, an optical amplifying medium is contained in the entire signal transmission core. In particular, an optical fiber amplifier using an organic optical fiber has a large core diameter, and therefore requires a very large excitation light power. Therefore, excitation has been performed using a pulse laser having a large output.

However, in the present embodiment, the core 50 for signal light transmission and the core 54 for pumping light are separated and the core 54 for pumping light is made thin, so that the optical amplifying medium can be used even if the power of the pumping light 302 is small. Excitable enough.

Since the excitation light core 54 is thin, the excitation light 302
The power density can be increased even if the power is low, and CW laser light can be used as the pump light 302. Since the optical amplifying medium can be always excited by exciting using the CW laser, the amplification can be performed regardless of the modulation frequency of the signal light 300. Since the signal light 300 propagates through the core 50 having a large diameter, position adjustment for light incidence on the core 50 is easy, and connection can be made in a short time.

Further, since the optical amplifying unit 56 is disposed in the excitation light core 54 in a dispersed manner, the excitation light 302 propagates through the excitation light core 54 over a long distance. Since the signal light beam 304 concentrates on the optical amplifier 56, the signal light 300 can be efficiently amplified without being dispersed throughout the pump light core 54.

Although FIG. 1 shows that the optical amplification section 56 is separated from the excitation light core 54, it is not necessary that the optical amplification section 56 be completely separated, and the optical amplification section 56 contains many organic dyes. You should do it. In the case where the signal light is made incident without being condensed, the optical amplification medium may be uniformly contained in the excitation light core 54.

FIG. 2 shows the refractive index distribution of the optical fiber in the radial direction. Cladding 52 diameter r _d, core diameter 50r _c, the excitation light core 54 diameter r _p. Although the refractive index n _c of the cladding 52 and the refractive index of the excitation light core 54 are constant at n ₀ ,
Is n for a radius r from the center of the fiber.
When expressed as (r), n (r) = n1 (1-Δ (r / r c) 2) (r p ≦ r ≦ r c) ... ( number _{1) Δ = (n 1 -n} c) / n It is formed so as to be close to ₁ and a quadratic function. Where n
_c <n ₁ <n ₀ . Since the refractive index of the core 50 is smaller than that of the excitation light core 54, the excitation light 302 is confined in the excitation light core 54, but the signal light 300 incident on the excitation light core 54 from the core 50 side is , Optical amplifier 56
After being amplified by, it returns to the core 50 again.

The signal light 300 to be focused by ^{_{l = π√ (r c 2 /}} 2Δ) ... period l expressed by equation (2), the optical amplifier unit 56 are arranged at intervals of period l.

If NA = n ₁ √ (2Δ) (Equation 3), the beam diameter φ at the position where the signal light 300 converges is approximately: φ = λ / NA (Equation 4). Accordingly, the diameter of the excitation light core 54 is φ
Degree, desirably φ〜3φ.

In this embodiment, n ₁ = 1.49, n ₁
Since -n _c = 0.015 and r _c = 0.25 mm were used, 1 = 5.5 mm, NA = 0.26, and φ = 2.3 μm.

In the present embodiment, by placing the ^{_{NA 2 = (n 0 2 -n}} 1 2) / n 0, the excitation light 302 is efficiently confined in the excitation light core 54 is incident on the excitation light core 54 numerical aperture NA _s of the excitation light, NA _s ≦ NA ₂ is desirable.

When the inclination of the incident signal light 300 with respect to the axis of the optical fiber amplifier 120 is θ, it is preferable that NA ₂ ≦ sin θ ≦ NA.

The first light amplifying section 56 from the light incident section is positioned at a distance of 1 from the light incident section. The length of the optical fiber amplifier 120 is determined according to the amplification factor. As in the present embodiment, since the core 50 is of the graded index type, it can be connected to the graded index optical fiber with high light transmission efficiency.

FIG. 3 shows a method of forming the optical amplifier 56 in the optical fiber of FIG. Ultraviolet light 510 is split by a beam splitter 504 into light beams having substantially the same amount of light. Each light beam is reflected by mirrors 500 and 502 and overlaps the same part. An interference portion 512 of each light is formed in the overlapped portion, and the intensity of the overlapped portion periodically changes like a sine function. In this interference part 512, a resin filled with an ultraviolet curable resin containing an organic dye in a hollow resin tube is placed.

As shown in FIG. 4, a periodic intensity distribution occurs at the overlapping portion of the light beams due to interference. The ultraviolet curable resin starts to cure from the place where the light intensity is strong. However, the organic dye is easily removed from the cured portion and is concentrated and confined in a place where the light intensity is weak, and becomes the light amplification portion 56.

Thus, the concentration distribution of the organic dye can be periodically formed. After that, the uncured portion is cured by the heat treatment to form the excitation light core 54. In this example, the dye concentration at the center of the excitation section was 25 ppm.

A method for producing an organic optical fiber having a graded index type refractive index distribution is described, for example, in Appl.
ied Optics Vol 33, p4261 (19
1994) can be used.

That is, the low molecular weight compound benzyln-butyl phta
late, polymerization initiator 1,1-bis (t-butylperoxy) 3,5,5-trimet
A methyl methacrylate monomer solution containing hylcyclohexane and dimethyl sulfoxide is poured into a hollow polymethyl methacrylate tube, and the tube is polymerized while rotating in a drier at about 95 ° C., followed by heat treatment under reduced pressure. .

Prior to the polymerization, the excitation light core 54 including the optical amplifier 56 formed in advance is positioned at the center of the polymethyl methacrylate tube, and the polymerization is performed. Thus, an organic optical fiber amplifier having a double structure including 56 can be formed.

The organic optical fiber amplifier must have an appropriate length, and after forming an organic optical fiber amplifier structure using a large-diameter polymethyl methacrylate tube, it is subjected to thermal stretching to obtain a desired aperture. And the length of the organic optical fiber amplifier.

As described above, when performing the thermal stretching, the cycle of the optical amplifier 56 in the excitation light core 54 which is formed in advance is formed short so as to have a desired cycle after the stretching.

Further, besides the above-mentioned thermal polymerization method, “Pol
ymers for Lightwave and I
integrated Optics "edited b
y Lawrence A. Hormark, Mark
el Dekker, Inc. Pp. 95-100
As described in (1992), a method for producing a graded index type organic optical fiber such as a polymerization method using ultraviolet rays may be appropriately selected.

FIG. 5 shows the configuration of an optical fiber amplifier according to another embodiment of the present invention. As shown in FIG. 5, in the present embodiment, the excitation light core 54 is provided at a position shifted from the center of the circular core 50 for transmitting the signal light.

The signal light 300 is the signal light incident fiber 2
4, the light is made to enter a position symmetrical to the excitation light core 54 with respect to the center of the core 50.

The excitation light 302 is the excitation light incident fiber 2
The light enters the excitation light core 54 through 8 and is extracted from the excitation light emitting fiber 30.

The diameter of the signal light incidence fiber 24 is
The signal light 300 incident on the core 50 is periodically collected by the graded index type refractive index distribution of the core 50. The light amplifying unit 5 is located at a position where the light is focused on the excitation light core 54.
6 is provided.

In the present embodiment, the position of the optical amplifying unit 56 is the first one at the position 1 from the end of the light incident unit,
Provided for 1 cycle. Further, when the length is adjusted so that the end of the fiber comes to the position of l from the last optical amplifier 56,
The signal light 300 is focused on the end of the fiber.

Therefore, similarly to the signal light inputting fiber 24, the signal light emitting fiber 26 is located at a position symmetrical to the excitation light core 54 with respect to the center of the core 50, so that the diameter of the signal light emitting fiber 26 is smaller than the core 50. The signal light 300 can be efficiently coupled to the small signal light emitting fiber 26.

That is, a multi-mode fiber having a core diameter of about 50 μm or a core diameter of about 7 mm for a core diameter of about 1 mm.
Light can be amplified by being provided between single-mode fibers of about μm.

In the case where an amplifying dye is dispersed in the entire core as in a conventional organic optical fiber amplifier, the incident light is of the present embodiment at a short distance after light incidence due to a graded index type refractive index distribution. However, due to defects in the core and at the interface between the core and the clad, distribution of refractive index, fluctuation of refractive index due to temperature, non-uniformity of diameter change, etc., the trajectory of light rays obtained from geometrical optics Deviation from

During transmission through an optical fiber of about 1 m, the light-collecting state at the time of incidence is completely destroyed, and the light intensity distribution is in an equilibrium state determined by electromagnetics regardless of the position of the optical fiber. Even before reaching this equilibrium,
The signal light 300 is no longer focused on a minute spot, and cannot be efficiently coupled to the small-diameter signal light fiber again.

On the other hand, in the present embodiment, even if the propagation is disturbed due to the non-uniformity during the transmission between the optical amplifiers,
Since only the signal light 300 incident on the optical amplifier 56 is amplified again, light that has not entered the optical amplifier due to disturbance is absorbed and attenuated while propagating through the core. In other words, since the signal light is sequentially transmitted with the light amplifying section 56 as a light emitting point, even after propagating through the optical fiber amplifier 120 to a desired distance, it is condensed again and efficiently coupled to the small-diameter signal light fiber. You.

Further, the light generated by the spontaneous emission in the optical amplifier 56 has no correlation with the signal light 300 and becomes noise. However, in the optical fiber amplifier 120 of the present invention, part of the spontaneous emission light is pumped. Like the light 302, the light is confined in the excitation light core 54 and taken out together with the excitation light 302, so that spontaneous emission light detected simultaneously with the signal light 300 is reduced, and as a result, noise is reduced.

FIG. 6 shows the configuration of an optical fiber amplifier according to another embodiment of the present invention. As shown in FIG. 6, in the present embodiment, in addition to the embodiment in FIG. 5, another signal light 301 is amplified, and the same components as those in FIG. 5 are denoted by the same reference numerals. Circular core 5 for transmitting signal light 300
The excitation light core 54 is provided at a position shifted from the center of 0.

The signal light 300 is the signal light incident fiber 24
Thus, the signal light 301 is transmitted from the signal light incident fiber 25
The light is incident on the core 50. With respect to the center of the core 50, the light is incident on a position symmetrical to the excitation light core 54. Excitation light 30
2 enters the excitation light core 54 through the excitation light incidence fiber 28 and is extracted from the excitation light emission fiber 30.

The excitation light core 54 is thicker than that of FIG. The signal light 300 and the signal light 301 are periodically collected by the graded index type refractive index distribution of the core 50. An optical amplifier 56 is provided at a position where the signal light is focused on the excitation light core 54.

Similarly to the signal light incident fiber 24, the signal light emitting fiber 26 is located at a position symmetrical to the excitation light core 54 with respect to the center of the core 50, whereby a signal having a smaller diameter than the core 50 is formed. The signal light 300 can be efficiently coupled to the light emitting fiber 26.

Similarly, the signal light emitting fiber 27 is positioned symmetrically with respect to the center of the core 50 with respect to the excitation light core 54. Since the diameter of the pump light core 54 is large, both the signal light 300 and the signal light 301 enter the optical amplifier 56 and are amplified. In this embodiment, it is desirable that the signal light 300 and the signal light 301 have different wavelengths.

The signal light 3 from the signal light emitting fiber 26
Even if there is a crosstalk where another signal light 301 is mixed with the signal light 301 or the signal light 300 is mixed with the signal light 301 from the signal light emitting fiber 27, the wavelength separation filter is used because the wavelengths are different. And the like can be used to remove extra wavelengths and reduce crosstalk. In this case, it is necessary to select a wavelength having a gain in the dye contained in the optical amplification unit 56 for each wavelength.

According to this embodiment, two signal lights can be amplified using one optical fiber amplifier 120, and a plurality of signal lights can be amplified by further increasing the number of signal lights.

In addition to this embodiment, a plurality of excitation light cores may be provided in one optical fiber amplifier. A signal light input fiber and a signal light output fiber may be provided at positions symmetrical with respect to the centers of the cores, corresponding to the respective excitation light cores. In this case, the organic dye contained in the optical amplification section of the corresponding excitation light core may be changed according to the wavelength of the signal light incident on the signal light incidence fiber.

FIG. 7 shows an embodiment of an optical fiber type optical amplifier using the optical fiber amplifier of the present invention. Excitation light source 1
An incident part 5 for receiving the pumping light 302 and the signal light 300 from the optical fiber 22; an optical amplifying part 6 for amplifying the signal light 300 which is also incident by the incident pumping light 302;
And an emission unit 7 for emitting the amplified signal light 300.

The incident section 5 includes a connector 150, a coupler 14
0, 141 and the incident light detector 130, and the optical amplifier 6 is constituted by the optical fiber amplifier 120 described with reference to FIG. The emitting unit 7 includes couplers 142 and 143,
The signal light 300, which includes the emission light detector 131 and the connector 150, enters through the connector 150.
The light amount of the signal light 300 is partially branched by the coupler 140 and detected by the incident light detector 130.

The excitation light 3 emitted from the excitation light source 122
02 enters the optical fiber amplifier 120 by the coupler 141. Since the diameter of the incident light fiber of the incident part 5 is small, the incident light fiber is connected using the coupler 141 so as to come to a predetermined position of the core 50 of the optical fiber amplifier 120 that propagates the signal light 300. The signal light 300 is amplified by the optical fiber amplifier 120.

Thereafter, the excitation light 302 is separated by the coupler 142. The pumping light 302 is separated from the signal light 300 and propagates in the pumping core. Therefore, the pumping light 302 can be easily extracted on the emission side without using optical components such as wavelength separation.
The coupler 142 is connected to a small-diameter light emitting fiber using a coupler 142.

A part of the amplified signal light 300 is
The light is partially branched by 43 and detected by the output light detector 131. The excitation light intensity is controlled based on the signal light intensity detected by the emission light detector 131 so that the signal light intensity becomes a predetermined intensity. The signal light 300 is extracted through the connector 151.

The reflected light from the output side is
If there is a problem in that the light is incident on the light and is amplified again, an isolator may be provided in front of the coupler 142. If it is a problem that the spontaneous emission light generated by the optical fiber amplifier 120 propagates to the incident side, an isolator may be provided behind the coupler 141.

Further, when it is necessary to monitor the reflected light from the emission side, a coupler may be provided behind the coupler 143 to separate the reflected light, and the separated light may be detected.

In this embodiment, a forward pump arrangement in which pump light is incident from the signal light incident side is used, but a backward pump in which pump light is incident from the output side, or a double-sided pump in which pump light is incident from both sides is used. Is also good.

FIG. 8 shows an embodiment of an optical amplification module for bidirectional communication used between a quartz optical fiber and a plastic optical fiber using the optical fiber amplifier of the present invention. The signal light of 780 nm from the single mode quartz fiber 22 enters the directional coupler 170.

The directional coupler 170 includes a dichroic mirror 17 that transmits a 780 nm signal light and reflects a 830 nm signal light to a two-branch coupler made of a silica-based waveguide.
2 is provided, and the signal light of 780 nm incident from the left enters the optical fiber type optical amplifier 10.

The optical fiber type optical amplifier 10 has the structure shown in FIG. 7, and is configured to amplify a signal light of 780 nm. The signal light amplified by the optical fiber type optical amplifier 10 is output to the plastic fiber 20 through the directional coupler 171.

The directional coupler 171 is provided with a dichroic mirror 173 that transmits a signal light of 780 nm and reflects a signal light of 830 nm to a two-branch coupler formed of a plastic waveguide. As the signal light waveguide, the directional coupler 171, and the plastic fiber 20 of the optical fiber type optical amplifier 10, those having a small numerical aperture of about 0.3 are used.

When transmitting a signal from the plastic fiber 20 side, a signal light of 830 nm is transmitted by the directional coupler 17.
1 and is reflected by the dichroic mirror 173 and output to the optical fiber type optical amplifier 11 side.

The signal light from the directional coupler 171 is condensed by the lens 180, and is condensed by the optical fiber type optical amplifier 11
Incident on. The signal light from the directional coupler 171 is condensed by the lens 180 and is
Incident on.

The optical fiber type optical amplifier 11 has a wavelength of 830 nm.
Has been adjusted to amplify the light of the signal light waveguide section,
A large numerical aperture of about 0.6 is used.

As a result, the light condensed minutely by the lens 180 can be efficiently transmitted to the optical fiber type optical amplifier 11.
Incident on. Since the length of the signal light amplified by the optical fiber type optical amplifier 11 is adjusted so as to be focused on the end face of the fiber of the optical fiber type optical amplifier 11, the directional coupler having a small core diameter is used. 171 can be efficiently coupled to the optical waveguide without using an optical component such as a lens.

The signal light amplified by the optical fiber type optical amplifier 11 is reflected by the directional coupler 171 at the dichroic mirror 172 and output to the quartz fiber 22.

FIG. 9 shows an embodiment of an optical information communication path using the optical fiber amplifier of the present invention. As shown in FIG. 9, an embodiment is shown in which information is bidirectionally communicated by optical fiber from the terminal station 400 of the telephone station to the home 402, but it is similarly used for distribution of a cable television or the like. be able to.

The terminal station 400 sends 78 to the quartz fiber 22.
A signal light having a wavelength of 0 nm is incident. The signal light incident on the quartz fiber 22 is amplified by the optical amplifier module for two-way communication 14 near the home 402 to which the signal is distributed.
It is divided into 16 by the coupler 100. The optical amplification module 14 for bidirectional communication uses the one shown in FIG.

The signal light divided into 16 is transmitted to each home 402 one by one by the plastic optical fiber 20.
In the home 402, the optical network unit 102
And receive the signal.

The signal from the home 402 uses light of 830 nm, the signal light enters the plastic optical fiber 20 from the optical network unit 102, and the star coupler 10
After the signals from the respective homes 402 are put together by 0, the signals are amplified by the optical amplification module 14 for two-way communication, incident on the quartz fiber 22, and reach the terminal station 400.

The difference between the core diameters of the quartz fiber 22 and the plastic optical fiber 20 is eliminated at the connection between the quartz fiber 22 and the optical amplification module 14 for bidirectional communication. Light can be efficiently transmitted from the optical fiber to the quartz fiber 22 having a small core diameter.

Since the light is split by the star coupler 100, the amount of light distributed to each home is reduced and the light is attenuated by the light absorption of the plastic optical fiber 20, but the signal is amplified by the optical amplification module 14 for bidirectional communication. By amplifying the light, a sufficient amount of light signal can be sent to each home 402.

In addition, by using near-infrared wavelength light with relatively little absorption in both the quartz fiber 22 and the plastic optical fiber 20, light having the same wavelength can be used from the terminal station 400 to the home 402. ,
As in the present embodiment, the signal can be amplified as it is as light and distributed to the home 402.

Further, since the signal is amplified as light, the configuration of the amplifier is simplified. Further, there is no need to change the light wavelength between the quartz fiber 22 and the plastic optical fiber 20, and there is no need to convert an optical signal into an electric signal and convert it into light having a different wavelength again, so that the structure is simplified and the light emitting element is simplified. The reliability is high because the number is small.

In addition, a quartz fiber 22 having little light absorption is used for the long distance portion, and a cheap plastic fiber 20 having a large core diameter can be used on the home side having many optical connection portions. Connection is easy, and a low-cost optical communication network can be constructed.

The optical fiber amplifier of the present invention can be used as a repeater in information communication such as a local area network using a plastic optical fiber other than the optical information communication path. In this case, unlike an amplifying device in which signal light is once converted to an electric signal, then amplified and then converted back to signal light, the signal can be amplified as it is, so that the structure of the repeater is simplified and the increase in noise due to relaying is reduced. Can be reduced.

[0097]

According to the present invention, it is possible to provide an optical fiber amplifier which can amplify signal light with low pumping power and can easily input signal light.

Further, by using this optical fiber amplifier, it is possible to provide an optical fiber type optical amplifier having a simple structure and high reliability.

Further, by using this optical fiber type optical amplifier, a low-cost optical information communication path can be constructed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical fiber amplifier according to one embodiment of the present invention.

FIG. 2 is a diagram showing a refractive index distribution in a radial direction of the optical fiber of FIG. 1;

FIG. 3 is a diagram illustrating a method of forming an optical amplifier in the optical fiber of FIG. 1;

FIG. 4 is a diagram illustrating the principle of formation of the optical amplification unit in FIG. 3;

FIG. 5 is a configuration diagram of an optical fiber amplifier according to another embodiment of the present invention.

FIG. 6 is a configuration diagram of an optical fiber amplifier according to another embodiment of the present invention.

FIG. 7 is a diagram showing an embodiment of an optical fiber type optical amplifier using the optical fiber amplifier of FIG. 5;

8 is a diagram showing an embodiment of an optical amplification module for bidirectional communication using the optical fiber type optical amplification device of FIG. 7;

9 is a diagram showing an embodiment of an optical information communication path using the optical amplification module for bidirectional communication of FIG.

[Explanation of symbols]

5 incident part, 6 optical amplification part, 7 emission part, 10, 11 ...
Optical fiber type optical amplifying device, 20: plastic optical fiber, 22: quartz fiber, 24, 25: signal light incidence fiber, 26, 27: signal light emission fiber, 28: excitation light incidence fiber, 30: excitation light Emission fiber, 5
0: core, 52: clad, 54: core for excitation light, 56
... Optical amplification unit, 60 ... Photopolymerizable resin, 100 ... Star coupler, 102 ... Optical network unit, 120 ... Optical fiber amplifier, 122 ... Excitation light source, 130 ... Incident light detector, 131 ... Outgoing light detection Vessels, 140, 141, 142,
143 coupler, 150, 151 connector, 160,
161, isolator, 170, 171 directional coupler, 172, 173 dichroic mirror, 180, lens, 300, 301 signal light, 302 excitation light, 30
4 ... Signal beam, 400 ... Terminal station, 402 ... Home, 50
0,502: mirror, 504: beam splitter, 51
0 ... ultraviolet rays, 512 ... interference part,

Claims (10)

[Claims] 1. An optical fiber amplifier for amplifying signal light similarly incident on said optical fiber by pumping light incident on said optical fiber, said optical fiber comprising: a first core at a central portion; A second core provided around the core and having a lower refractive index than the first core; and a second core provided around the second core.
And the cladding having a lower refractive index than the core, the pumping light propagates in the first core to excite an optical amplification medium contained in the first core, and the signal light is 2
An optical fiber amplifier, which propagates in the core of (1) and is amplified by the excited optical amplifying medium. 2. The optical fiber amplifier according to claim 1, wherein said optical amplifying medium is arranged in said first core at a periodic interval with respect to a traveling direction of said pumping light. 3. The optical fiber amplifier according to claim 1, wherein said second core is formed so that said refractive index decreases from a central portion toward an outer peripheral portion. 4. An optical fiber amplifier according to claim 1, wherein said second core focuses said signal light on said optical amplification medium. 5. The optical fiber amplifier according to claim 1, wherein said first core and said second core are formed of an organic material having optical transparency. 6. An optical fiber amplifier according to claim 1, wherein said optical amplification medium is an organic dye. 7. An incident section for receiving pumping light and signal light from a pumping light source, an optical amplifying section for amplifying the incident signal light by the incident pumping light, and the pumping light and the amplifier. 7. An optical fiber type optical amplifying device comprising: an emission unit for emitting a selected signal light; wherein the optical amplification unit is any one of claims 1 to 6.
An optical fiber type optical amplifying device characterized in that it is the optical fiber amplifier according to the above item. 8. The optical amplifier according to claim 7, wherein said second core of said optical amplifier for transmitting said signal light has a core diameter smaller than a diameter of said second core at said incident part or said emission part. An optical fiber type optical amplifying device connected to a fiber. 9. An optical information communication path for transmitting an optical signal using a bidirectional communication optical amplification module for connecting an optical fiber having a core material of quartz and an optical fiber having a core material of an organic material, 9. An optical information communication path, wherein the bidirectional communication optical amplification module is the optical fiber type optical amplification device according to claim 7. 10. An optical amplification method for amplifying a signal light by exciting an optical amplification medium contained in an optical fiber with excitation light, wherein said excitation light is propagated to a first core of said optical fiber and said optical fiber is Amplifying the signal light by propagating the signal light to the second core and condensing the signal light on the optical amplification medium.