JP2001021755A - Multiple wavelength signal transmitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive multiple wavelength signal transmitting device having a light absorbing band outside an allowance range with respect to a wavelength position of a prescribed wavelength to utilize a bandpass filter not suitable for use, and to enhance using efficiency of the bandpass filter. SOLUTION: This device comprises a double core optical fiber DF3, collimator lenses L3, L11, bandpass filters F3, F11, and light receivers R3, R11. A filter exhibiting an absorption spectrum shifted in a peak position of light absorption band with respect to a wavelength position of a light signal of a prescribed wavelength is used as the bandpass filters F3, F11, and at least one means out of the collimator lenses L3, L11 having a focal distance where an incident angle of the light siganl incident from the optical fiber DF3 into the bandpass filters F3, F11 are selscted to conform the peak position of the light absorbing band exhibited by the bandpass filters F3, F11 in the incident angle to a wavelength position of the light signal of the prescribed wavelength, and the double core optical fiber DF3 adjusted in an interoptical path distance is used, in the device of the present invention.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-wavelength signal transmission device for optical communication used for separating (demultiplexing) an optical signal having a desired wavelength from a multi-wavelength signal. The present invention particularly relates to a multi-wavelength signal transmission device including a two-core optical fiber, a collimator lens, a bandpass filter, and a light receiver.

[0002]

2. Description of the Related Art Optical fiber communication technology is used for communication networks using personal computers such as telephones, faxes, and, in recent years, the Internet. According to this technology, information such as image, sound, and character data is temporarily converted into an electric signal (digital signal), which is further converted into an optical signal (13).
It uses a method of transmitting through an optical fiber instead of a semiconductor laser light having a wavelength in the range of 00 to 1550 nm), and a large amount of information can be transmitted at a time by putting various kinds of optical signals having different wavelengths into one optical fiber. In addition, there is an advantage that transmission can be performed over a long distance.

In order to use the optical fiber communication technology more efficiently, a technology (multiplexing technology) for combining as much information as possible (an optical signal composed of a plurality of laser beams having different wavelengths) or a multiplexed technology. It is necessary to develop a technology for separating (demultiplexing) only desired information from the plurality of pieces of information. In particular, as the amount of information increases, the wavelength interval between optical signals transmitted through a single optical fiber must be set to be narrow. Therefore, the development of a technique for accurately separating a desired optical signal from these optical signals has progressed. In.

[0004] In order to separate an optical signal having a desired wavelength from a multi-wavelength signal, various multi-wavelength signal transmission devices have been proposed. For example, US Pat. No. 5,583,683 discloses an optical fiber, a collimator lens, a bandpass filter,
An apparatus including a light receiver is disclosed. But,
Since the optical fiber used in this device is a single-core optical fiber (single-mode fiber), when the amount of optical signals to be separated increases, a corresponding number of devices are required, and the device as a whole is required. There is a disadvantage that the size is increased.

[0005] As an example in which the size of the apparatus can be reduced as a whole, a multi-wavelength signal transmission apparatus shown in FIGS. 5 and 6 has been proposed. FIG. 5 shows optical signals having different wavelengths (first to fourth optical signals in the figure) emitted from the two-core optical fiber, which are transmitted to the multi-wavelength signal transmission devices D ₁₁ , D ₁₂ ,
The procedure one by one separated from the first optical signal and the fourth optical signal in order using the D ₁₃ and D ₁₄ is a diagram schematically showing.
The Figure 6 is a diagram schematically showing an enlarged multiwavelength signal transmission apparatus D ₁₁ for separating only the first optical signal therein. As shown in FIGS. 5 and 6, the multi-wavelength signal transmission devices D ₁₁ , D ₁₂ , D _13, and D ₁₄ arranged in order are two-core optical fibers OF ₁₁ , OF ₁₂ , OF ₁₃ , OF ₁₄ , and OF ₁₄ , respectively. lens _{L 11, L 12, L 13} , and L _14, and a band filter _{F 11, F 12, F 13} , and F ₁₄ and the light receiver _{R 11, R 12, R 13} , and R _14,. Then, two or more optical signals having different wavelengths (first
To the fourth optical signal: wavelengths: λ ₁₁ , λ ₁₂ , λ ₁₃ , and λ ₁₄ ), the first optical signal λ ₁₁ is first separated by the multi-wavelength signal transmission device D ₁₁ . Two-core optical fiber OF ₁₁ emitted light signal from the end of the outgoing optical transmission for the optical path 11a of the (fourth light signal from the first) is transmitted through the collimator lens L _11, thereby being converged. The converged optical signal is
Incident on the band-pass filter F ₁₁ arranged at the focal point of the collimator lens. Band filter F ₁₁ causes only transmits the first optical signal, without transmitting the other light signal (second to fourth optical signal) having a reflection characteristic, different wavelengths very close It is manufactured so that only an optical signal of one wavelength among the optical signals can be transmitted and separated.
The transmitted first optical signal λ ₁₁ is received by the light receiver R ₁₁ . On the other hand, optical signals other than the first optical signal (second to fourth optical signals)
Optical signal) is reflected, via the collimator lens L ₁₁ again, the two-core reflected light optical path for transmitting the first optical fiber OF ₁₁
1b. Second to fourth optical signal returned to the reflected light optical path for transmitting an 11b is then transmitted to the arranged multiwavelength signal transmission device D ₁₂ was, the second optical signal lambda ₁₂ are separated here. In such a procedure, the four optical signals having different first to fourth wavelengths are converted into the first optical signal λ ₁₁ by the multi-wavelength signal transmission devices D ₁₁ , D ₁₂ , D ₁₃ and D ₁₄ arranged in order.
To the fourth optical signal λ ₁₄ .

[0006] Production of multi-wavelength signal transmission apparatus D ₁₁ shown in FIG. 6, first placing the two-core optical fiber collimator lens L ₁₁ which transmits converging the optical signal emitted from the end portion of the outgoing optical transmission for the optical path 11a of the OF ₁₁ and, then, the band-pass filter F ₁₁ that transmits only the first optical signal among the transmission converged optical signal at the collimator lens is arranged at the focal point of the collimator lens (focal length f _11), further band-pass filter It has been made in the procedure of placing the light receiver R ₁₁ for receiving the first optical signal transmitted through the. Then conventionally, as the collimator lens L _11, an optical signal transmitted through convergence is using those designed to be incident on the band-pass filter at a fixed angle of incidence (approximately 1 °). As the band-pass filter F _11,
To transmit only the first optical signal is is used (the peak position of the light absorption band of the bandpass filter is so to match the wavelength lambda ₁₁ of the first optical signal) as prepared. However, in consideration of the fluctuation width of the wavelength lambda ₁₁ (fluctuation width of the center wavelength of the laser beam emitted from the semiconductor laser as a light source), band pass filter, is typically the wavelength tolerance with respect to the peak position of the light absorption band Those designed to be ± 0.1 nm are used. However, it is difficult to stably and mass-produce the bandpass filter having the light absorption band only in such a narrow range. Therefore, it is difficult to provide the bandpass filter having the desired light absorption band at a low cost. There is a problem.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a filter which has an optical absorption band outside a permissible range with respect to the wavelength position of an optical signal having a predetermined wavelength and which is not suitable for use. An object of the present invention is to provide a multi-wavelength signal transmission device at low cost by increasing the use efficiency of such a filter.

[0008]

Means for Solving the Problems The present inventor paid attention to the transmission wavelength shift characteristic with respect to the incident angle of the bandpass filter and studied. As a result of the examination, the present inventor uses a bandpass filter that shows an absorption spectrum in which the peak position of the light absorption band is shifted with respect to the wavelength position of the optical signal of the predetermined wavelength, and the light incident on the bandpass filter from the two-core optical fiber. The focal length of the collimator lens is adjusted so that the incident angle of the signal is such that the peak position of the light absorption band indicated by the bandpass filter at the incident angle coincides with the wavelength position of the optical signal having the predetermined wavelength (that is, the focal length of the collimator lens is adjusted). Using a collimator lens having a focal length selected to have such an incident angle), or adjusting the distance between the optical paths for transmitting the reflected light and transmitting the reflected light of the two-core optical fiber (that is, adjusting the distance between the optical paths). Use a two-core optical fiber whose distance between optical paths is adjusted to achieve such an incident angle) or a collimator lens whose focal length is determined and a two-core fiber whose distance between optical paths is adjusted By using a combination of the fibers were found to be able to effectively use the band-pass filter that was not suitable for use.

That is, when the incident light is perpendicular to the surface of the bandpass filter, the bandpass filter is manufactured so as to have an absorption band slightly longer than a predetermined wavelength, and the bandpass filter has a predetermined wavelength. The wavelength of the optical signal that passes through the bandpass filter at that angle of incidence is determined by calculating the angle of incidence to obtain the angle of incidence and using a collimator lens with a focal length selected to match the angle of incidence. By adjusting the bandpass filter to be located at the peak position of the indicated absorption band, a bandpass filter that has conventionally been able to use only a filter having an absorption band within a very narrow allowable range for an optical signal of a predetermined wavelength has a desired absorption band. We found that it can be used as a bandpass filter. Therefore, a bandpass filter having an absorption band other than the allowable range that has not been used as a non-applicable product can be used efficiently, for example, by using a selected collimator lens, thereby dramatically increasing the productivity of the bandpass filter. Can be raised.

The present invention relates to a two-core optical fiber having an outgoing light transmitting optical path for transmitting two or more optical signals having different wavelengths and a reflected light transmitting optical path, and an end of the outgoing light transmitting optical path of the two-core optical fiber. A collimator lens that transmits and converges the optical signal emitted from the unit, is disposed at the focal point of the collimator lens, transmits the collimator lens, transmits only the optical signal of a predetermined wavelength among the converged optical signals, and A multi-wavelength signal transmission device comprising a bandpass filter that does not transmit an optical signal of a wavelength, and a photodetector that receives an optical signal transmitted through the bandpass filter, wherein the bandpass filter is located at a wavelength position of the optical signal having a predetermined wavelength. A band-pass filter showing an absorption spectrum with a shifted peak position of the light absorption band is used, and the band-pass filter is formed from a two-core optical fiber as the collimator lens. Angle of incidence of the light signal entering the filter is,
Multi-wavelength signal transmission using a collimator lens having a focal length selected so that a peak position of a light absorption band indicated by the bandpass filter at the incident angle coincides with a wavelength position of an optical signal having a predetermined wavelength. In the device.

The present invention also provides a two-core optical fiber having an outgoing light transmitting optical path for transmitting two or more optical signals having different wavelengths and a reflected light transmitting optical path, and an outgoing light transmitting optical path of the two-core optical fiber. A collimator lens that transmits and converges an optical signal emitted from an end portion, is disposed at a focal point of the collimator lens, transmits only the optical signal of a predetermined wavelength among the converged optical signals, and A multi-wavelength signal transmission device comprising a bandpass filter that does not transmit an optical signal having a wavelength of, and a light receiver that receives an optical signal transmitted through the bandpass filter, wherein the bandpass filter is disposed at a wavelength position of an optical signal having a predetermined wavelength. Using a band-pass filter that shows an absorption spectrum in which the peak position of the light absorption band is shifted, and the band from the two-core optical fiber is used as the two-core optical fiber. The optical path for emitting light transmission and the reflected light transmission are such that the incident angle of the optical signal incident on the filter is such that the peak position of the light absorption band indicated by the bandpass filter at the incident angle matches the wavelength position of the optical signal of the predetermined wavelength. There is also a multi-wavelength signal transmission device characterized by using a two-core optical fiber whose distance from the optical path for use is adjusted.

Further, the present invention provides a two-core optical fiber having an outgoing light transmitting optical path and a reflected light transmitting optical path for transmitting two or more optical signals having different wavelengths from each other, and an outgoing light transmitting optical path of the two-core optical fiber. A collimator lens that transmits and converges an optical signal emitted from an end of the collimator lens, is disposed at a focal position of the collimator lens, and transmits through the collimator lens;
A multi-wavelength signal transmission device including a bandpass filter that transmits only an optical signal of a predetermined wavelength out of converged optical signals and does not transmit optical signals of other wavelengths, and a photodetector that receives an optical signal transmitted through the bandpass filter. A band filter that shows an absorption spectrum in which a peak position of an optical absorption band is shifted with respect to a wavelength position of an optical signal having a predetermined wavelength is used as the band filter, and a two-core optical fiber and a collimator lens are used as the two-core optical fiber. The incident angle of the optical signal entering the bandpass filter from the optical fiber is adjusted so that the peak position of the light absorption band indicated by the bandpass filter at the incident angle coincides with the wavelength position of the optical signal having the predetermined wavelength. The two-core optical fiber that adjusts the distance between the optical path for transmitting light and the optical path for transmitting reflected light and determines the focal length of the collimator lens There is also a multi-wavelength signal transmission apparatus which comprises using a combination of a meter lens.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, a multi-wavelength signal transmission device according to the present invention comprises a two-core optical fiber, a collimator lens, a bandpass filter, and a light receiver. The apparatus of the present invention uses, as a bandpass filter, a bandpass filter that shows an absorption spectrum in which a peak position of an optical absorption band is shifted with respect to a wavelength position of an optical signal having a predetermined wavelength,
And the incident angle of the optical signal to the bandpass filter has a focal length selected such that (1) the peak position of the light absorption band indicated by the bandpass filter at the incident angle matches the wavelength position of the optical signal of the predetermined wavelength. Using a collimator lens, or (2)
Two cores in which the distance between the output light transmission optical path and the reflected light transmission optical path is adjusted such that the peak position of the light absorption band indicated by the bandpass filter at the incident angle matches the wavelength position of the optical signal of the predetermined wavelength. Using optical fiber, or (3)
The distance between the optical path for transmitting the reflected light and the optical path for transmitting the reflected light of the two-core optical fiber is adjusted so that the peak position of the light absorption band indicated by the bandpass filter at the incident angle coincides with the wavelength position of the optical signal having the predetermined wavelength. The present invention is characterized in that a two-core optical fiber for which adjustment and determination of a focal length of a collimator lens are performed is used in combination with a collimator lens.

FIGS. 1 to 3 are diagrams schematically showing a multi-wavelength signal transmission apparatus according to the present invention constituted by introducing the characteristic means of the present invention shown in the above (1) to (3). is there. As shown in FIGS. 1 to 3, each of the multi-wavelength signal transmission devices D ₁ , D ₂ , and D ₃ includes two-core optical fibers OF ₁ , OF ₂ , and OF ₃ , and collimator lenses L ₁ , L ₂ , and L ₃ , band filters F ₁ , F ₂ , and F ₃ , and photodetectors R ₁ , R ₂ , and R ₃ . These functions are basically the same as those of the conventional device. That is, the two-core optical fiber has an optical path for transmitting outgoing light and an optical path for transmitting reflected light that transmit two or more optical signals having different wavelengths. The collimator lens has a function of transmitting and converging the optical signal emitted from the end of the optical path for transmitting the emitted light of the two-core optical fiber. The bandpass filter is disposed at the focal point of the collimator lens, transmits only the optical signal of a predetermined wavelength among the converged optical signals, and reflects the optical signal of other wavelengths without transmitting the optical signal. Having. The light receiver has a function of receiving an optical signal having a wavelength transmitted through the bandpass filter.

FIG. 1 shows that the incident angle θ ₁ of the optical signal to the bandpass filter is selected such that the peak position of the light absorption band indicated by the bandpass filter at the incident angle coincides with the wavelength position of the optical signal having a predetermined wavelength. it is a multi-wavelength signal transmission apparatus using a collimator lens L ₁ having a focal length f ₁ shows schematically. In the example of FIG. 1, a conventional system (FIG. 6) shorter focal length than the collimator lens L ₁₁ which has been used in the f
And varying the incident angle theta ₁ of the optical signal to the bandpass filter F ₁ by using a collimator lens L ₁ with _1. still,
In this example, using the same as a two-core optical fiber OF _1, a two-core optical fiber OF ₁₁ used in conventional systems. When the bandpass filter is arranged at the focal point of the collimator lens selected in this way, the incident angle of the optical signal to the bandpass filter is such that the peak position of the light absorption band indicated by the bandpass filter at the incident angle is the optical signal of the predetermined wavelength. At the wavelength position. Therefore, by using, as a bandpass filter, a bandpass filter that shows an absorption spectrum in which the peak position of the light absorption band is shifted with respect to the wavelength position of the optical signal having the predetermined wavelength, in accordance with the incident angle of the optical signal to the bandpass filter, It becomes possible to separate an optical signal of a desired wavelength.

FIG. 2 shows that the incident angle θ ₂ of the optical signal to the bandpass filter F ₂ is such that the peak position of the light absorption band indicated by the bandpass filter at the incident angle coincides with the wavelength position of the optical signal of a predetermined wavelength. Optical path 2 for transmitting outgoing light of _two- core optical fiber OF 2
1 schematically shows a multi-wavelength signal transmission device configured using a two-core optical fiber in which the distance a ₂ between the optical path a and the reflected light transmission optical path 2b is adjusted. In the example of FIG. 2, the distance a ₂ between the optical path for transmitting the reflected light and the optical path for transmitting the reflected light of the two-core optical fiber is set to the distance for transmitting the emitted light of the two-core optical fiber used in the conventional system (FIG. 6). The incident angle θ ₂ of the optical signal to the bandpass filter is changed by increasing the distance a ₁₁ between the optical path 11a and the reflected light transmitting optical path 11b. In this example, as a collimator lens L _2, using conventional systems collimator lens having a collimating lens L ₁₁ and the same focal length f ₁₁ which has been used in (Fig. 6). By using the two-core optical fiber whose distance between the optical paths is adjusted as described above, the incident angle of the optical signal to the bandpass filter is such that the peak position of the light absorption band indicated by the bandpass filter at the incident angle is an optical signal having a predetermined wavelength. At the wavelength position. Therefore, as a bandpass filter,
By using a bandpass filter showing an absorption spectrum in which the peak position of the light absorption band is shifted with respect to the wavelength position of the optical signal of the predetermined wavelength, the optical signal of the desired wavelength can be adjusted according to the incident angle of the optical signal to the bandpass filter. Can be separated.

FIG. 3 shows the angle of incidence of the optical signal on the bandpass filter.
θ_ThreeIs the light absorption band indicated by the bandpass filter at that angle of incidence.
The peak position matches the wavelength position of the optical signal of the predetermined wavelength.
Thus, the outgoing light transmission optical path 3a and the reflected light transmission optical path 3b
Distance a_ThreeAdjusted two-core optical fiber OF_ThreeAnd focus
Distance f_ThreeCollimator lens L for which_ThreeCombined with
Schematically shows a multi-wavelength signal transmission device configured using
FIG. That is, as shown in the above (1) or (2)
By combining the means, the optical signal to the bandpass
The angle of incidence of the signal is changed. In the example of FIG.
As a bar, two-core optical fiber OF_ThreeOutgoing light transmission light
Distance a between path 3a and reflected light transmission optical path 3b_ThreeAnd
Dual-core optical fiber used in conventional system (Fig. 6)
-OF_{1 1}Between the optical path for transmitting the reflected light and the optical path for transmitting the reflected light
Optical fiber OF slightly wider than the distance of_ThreeFor
And the conventional system (6
Collimator lens L used in figure)₁₁Slightly more
Short focal length f_ThreeCollimator lens L with_ThreeUsing
And the incident angle θ of the optical signal to the bandpass filter_ThreeChange
I have. Thus, as shown in (1) or (2) above,
Light to the bandpass filter by combining
The angle of incidence of the signal is the light that the bandpass filter indicates at that angle of incidence.
The peak position of the absorption band coincides with the wavelength position of the optical signal of the predetermined wavelength.
Will be matched. Therefore, as a bandpass filter,
Peak position of light absorption band with respect to wavelength position of optical signal of wavelength
Use a bandpass filter that shows an absorption spectrum that is shifted.
To match the angle of incidence of the optical signal to the bandpass filter
Optical signal having a desired wavelength can be separated.
You.

The multi-wavelength signal transmission device of the present invention can be manufactured by selecting and arranging a two-core optical fiber, a collimator lens, a bandpass filter, and a light receiver according to the above-described optimization method. As these two-core optical fiber, collimator lens, bandpass filter, and light receiver, those conventionally used or those manufactured according to a conventionally known method can be used. The bandpass filter will be briefly described below.

The bandpass filter used in the present invention exhibits an absorption spectrum in which the peak position of the light absorption band is shifted from the wavelength position of an optical signal having a predetermined wavelength. As described above, the absorption spectrum in which the peak position of the light absorption band is shifted can be obtained by changing the incident angle of the optical signal to the bandpass filter. The angle of incidence of the optical signal on the bandpass filter is 8
° or less is appropriate. If the angle of incidence is set to be larger than this, the deflection-dependent characteristic becomes large, which is not practical. The shift of the peak position of this light absorption band is usually 0.1 to
It is in the range of 8.0 nm. The half-width of the wavelength in the absorption spectrum is adjusted according to the wavelength interval of the optical signal to be separated, but is preferably in the range of 0.1 to 2.0 nm in the apparatus of the present invention.

The bandpass filter used in the present invention can be manufactured according to a conventional manufacturing method. Specifically, the bandpass filter is formed by disposing a high-refractive-index material on a transparent dielectric (glass substrate) in the above-described target absorption (transmission) wavelength region by optical thickness (refractive index × geometric thickness). Is a layer having a predetermined wavelength λ (hereinafter, referred to as H) and a layer having a low refractive index material having an optical thickness of １ ／ of the predetermined wavelength λ (hereinafter, referred to as L). , HLH ... HLH, or HLH
.., A reflective layer having a layer structure composed of HL, etc., and HH, HH
, Or LL, LLLL,... Can be manufactured as a single- or multi-cavity multilayer film by laminating the cavity layers with even-numbered layers. Examples of high refractive index materials include Ta ₂
O ₅ , TiO ₂ , Nb ₂ O ₅ , HfO ₂ , ZrO ₂ , and Al
₂ O ₃ Si can be mentioned. Examples of the low refractive index material include SiO ₂ and MgF ₂ .

The bandpass filter used in the present invention is manufactured mainly by using a physical vapor deposition method (vacuum vapor deposition, reactive vapor deposition, ion plating, ion beam assisted vapor deposition, reactive sputtering, bias sputtering, etc.). Can be. In particular, a multilayer film having a narrow light absorption band such as a bandpass filter used in the present invention is an advantageous method for forming a multi-cavity type multilayer film having a very large total number,
For example, it is preferable to use a method including a process involving a process for increasing the film density, such as ion bombardment or plasma ion bombardment, such as ion plating, ion beam assisted deposition, and bias sputtering.

The manufacture of the bandpass filter is performed in the following procedure. First, a number of product substrates are arranged at substantially the same distance from the evaporation source of the evaporation material, and one of the film thickness control monitor substrates is arranged at a predetermined position. The control of the thickness of the layers deposited on a number of product substrates at the same time is performed by opening and closing the evaporation source shutter by measuring the increase or decrease of light due to the film deposited thereon by monitoring light passing through the monitor substrate.
That is, each time the amount of light transmitted or reflected by the film on the monitor substrate becomes maximum or minimum, its optical thickness becomes 1/4 of the wavelength of the monitoring light beam or an integral multiple thereof. The closing controls the thickness of the layer. By repeating such a method, it is possible to manufacture a single or multilayer cavity type multilayer film as described above.
Examples of the bandpass filter that can be used in the present invention include a triple cavity type multilayer film (83 layers) and a quadruple cavity type multilayer film (119 layers).

[0023]

EXAMPLES Examples of the present invention will be described below. (1) Production of bandpass filter and its characteristics A substrate support (glass plate) is placed on a rotating plate having a diameter of about 30 cm in a vacuum chamber having a diameter of 90 cm.
About 200 ° C, oxygen partial pressure in the tank: about 1.5 × 10 ^-4 (Torr)
Vapor deposition was performed by using an ion plating method under the conditions described in (1) to produce a bandpass filter (quadruple-cavity type multilayer film (119 layers)) according to the present invention having the following layer constitution. [(HL) ⁶ H (L) ⁶ H (LH) ⁶ ] L [(HL) ⁷ H
(L) ⁶ H (LH) ⁷ ] L [(HL) ⁷ H (L) ⁶ H (L
H) ⁷ ] L [(HL) ⁶ H (L) ⁶ H (LH) ⁶ ] H: high refractive index material (tantalum oxide (Ta ₂ O ₅ )) L: low refractive index material (silicon oxide (SiO ₂ ) FIG. 4 shows the obtained light absorption spectrum of the bandpass filter. The peak position (center wavelength) of the light absorption band with respect to the incident angle of this filter is as follows. Peak position of light absorption band at incident angle 0 °: 1550.0
nm Peak position of light absorption band at an incident angle of 1 °: 1549.9
nm Peak position of light absorption band at an incident angle of 2 °: 1549.5
9 nm Peak position of light absorption band at an incident angle of 3 °: 1549.0
9 nm

(2) Manufacture of Multi-Wavelength Signal Transmission Apparatus The multi-wavelength signal transmission apparatus of the present invention was manufactured by the following procedure using the bandpass filter manufactured as described above. Note that a photodetector having a photodetector capable of receiving laser light having a wavelength in the range of 1300 nm to 1550 nm was used. 1) A collimator lens having a focal length selected so that the angle of incidence of the optical signal on the bandpass filter coincides with the wavelength position of the optical signal of a predetermined wavelength at the angle of incidence of the optical absorption band indicated by the bandpass filter. In the case of manufacturing a multi-wavelength signal transmission device according to the present invention by using the optical fiber, a two-core optical fiber having an optical path distance of 1 mm between an optical path for transmitting outgoing light and an optical path for transmitting reflected light was used. If the wavelength of the optical signal having the predetermined wavelength is 1549.59 nm, the light absorption peak position of the bandpass filter coincides with the wavelength of the optical signal having the predetermined wavelength when the incident angle is 2 °. = 0.5 mm / focal length, the collimator lens has a focal length of 1
Select and use one with 4.32mm. Alternatively, if the wavelength of the optical signal having the predetermined wavelength is 1549.09 nm, in this case, the light absorption peak position of the bandpass filter coincides with the wavelength of the optical signal having the predetermined wavelength when the incident angle is 3 °. From the calculation formula of tan3 ° = 0.5 mm / focal length, a collimator lens having a focal length of 9.54 mm is selected and used. in this way,
By using a collimator lens having a selected focal length, a multi-wavelength signal transmission device according to the present invention can be manufactured. As the bandpass filter, a filter having an absorption spectrum in which the peak position of the light absorption band is shifted from the wavelength position of the optical signal having the predetermined wavelength can be used.

2) The angle of incidence of the optical signal on the bandpass filter is
The distance between the optical path between the outgoing light transmitting optical path and the reflected light transmitting optical path of the two-core optical fiber so that the peak position of the light absorption band indicated by the bandpass filter at the incident angle matches the wavelength position of the optical signal of the predetermined wavelength. In the case of manufacturing a multi-wavelength signal transmission device according to the present invention by using a two-core optical fiber adjusted for the following, a collimator lens having a focal length of 14.32 mm was used. If the wavelength of an optical signal having a predetermined wavelength is 15
When the wavelength is 49.59 nm, in this case, the light absorption peak position of the bandpass filter coincides with the wavelength of the optical signal having the predetermined wavelength when the incident angle is 2 °, so tan2 ° = half the distance between optical paths / 14. .32 mm, a two-core optical fiber having a distance between optical paths of 1 mm is selected and used. Alternatively, if the wavelength of the optical signal having the predetermined wavelength is 1549.09 nm, the light absorption peak position of the bandpass filter coincides with the wavelength of the optical signal having the predetermined wavelength when the incident angle is 3 °. From the formula of ° = half the distance between optical paths / 14.32 mm, the distance between optical paths is 1 mm as a two-core optical fiber.
Select and use those. As described above, the multi-wavelength signal transmission device according to the present invention can be manufactured by using the two-core optical fiber in which the distance between the optical path for transmitting the emitted light and the optical path for transmitting the reflected light is adjusted. As the bandpass filter, a filter having an absorption spectrum in which the peak position of the light absorption band is shifted from the wavelength position of the optical signal having the predetermined wavelength can be used.

3) The angle of incidence of the optical signal on the bandpass filter is
A two-core optical fiber in which the distance between the optical path for transmitting outgoing light and the optical path for transmitting reflected light is adjusted so that the peak position of the light absorption band indicated by the bandpass filter at the incident angle matches the wavelength position of the optical signal of the predetermined wavelength. And when a multi-wavelength signal transmission device according to the present invention is manufactured by using a collimator lens having a determined focal length in combination, assuming that the wavelength of an optical signal having a predetermined wavelength is 1549.59 nm, in this case, a bandpass filter Becomes equal to the wavelength of an optical signal of a predetermined wavelength when the light absorption peak position is at an incident angle of 2 °. Therefore, from the calculation formula of tan2 ° = half the distance between optical paths / focal length, for example, a collimator lens The one with a focal length of 11.43 mm is selected, and the one with a distance between optical paths of 0.8 mm is selected and used as a two-core optical fiber. Alternatively, if the wavelength of the optical signal having the predetermined wavelength is 1549.09 nm, in this case, the light absorption peak position of the bandpass filter coincides with the wavelength of the optical signal having the predetermined wavelength when the incident angle is 3 °.
From the formula of tan3 ° = half the distance between optical paths / focal length, for example, a lens having a focal length of 12.02 mm is selected as a collimator lens, and the distance between optical paths is 1 as a two-core optical fiber. .25 mm is selected and used. As described above, the multi-wavelength signal transmission device according to the present invention is provided by using the two-core optical fiber in which the distance between the output light transmission optical path and the reflected light transmission optical path is adjusted and the collimator lens in which the focal length is determined. Can be manufactured. As the bandpass filter, a filter having an absorption spectrum in which the peak position of the light absorption band is shifted from the wavelength position of the optical signal having the predetermined wavelength can be used.

[0027]

According to the multi-wavelength signal transmission device of the present invention, a band filter which has a peak position of an optical absorption band outside the allowable range of the wavelength of an optical signal having a predetermined wavelength and can not be used can be used. Therefore, the use efficiency of the bandpass filter can be remarkably increased, and stable production can be ensured, so that the bandpass filter can be manufactured at low cost. Further, since it becomes possible to manufacture such a bandpass filter, it can be said that the multi-wavelength signal transmission device of the present invention can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a multi-wavelength signal transmission device according to the present invention configured using a collimator lens having a selected focal length.

FIG. 2 is a diagram schematically showing a multi-wavelength signal transmission device according to the present invention, which is configured using a two-core optical fiber in which an optical path distance between an output light transmission optical path and a reflected light transmission optical path is adjusted.

FIG. 3 is a diagram illustrating a multi-wavelength signal transmission device according to the present invention configured using a collimator lens having a selected focal length, and a two-core optical fiber having an adjusted optical path distance between an optical path for transmitting outgoing light and an optical path for transmitting reflected light. It is the figure which showed typically.

FIG. 4 is a graph showing transmission wavelength (center wavelength) movement characteristics with respect to an incident angle of the bandpass filter according to the present invention.

FIG. 5 is a diagram schematically showing a procedure of separating four optical signals having different wavelengths one by one from a first optical signal to a fourth optical signal using a conventional multi-wavelength signal transmission device. is there.

FIG. 6 is a diagram schematically showing a configuration of a conventional multi-wavelength signal transmission device for separating only a first optical signal.

[Explanation of symbols]

D ₁ , D ₂ , D ₃ , D ₁₁ , D ₁₂ , D ₁₃ , D ₁₄ multi-wavelength signal transmission device OF ₁ , OF ₂ , OF ₃ , OF ₁₁ , OF ₁₂ , OF ₁₃ , OF ₁₃ , OF
₁₄ two-core optical fiber _{L 1, L 2, L 3} , L 11, L 12, L 13, L 14 collimator lens _{F 1, F 2, F 3} , F 11, F 12, F 13, F 14 band filter R ₁ , R ₂ , R ₃ , R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ Receiver 1a, 2a, 3a, 11a Outgoing light transmission optical path 1b, 2b, 3b, 11b of a two-core optical fiber Reflected light transmission of a two-core optical fiber Optical path

Claims (3)

[Claims] 1. A two-core optical fiber having an outgoing light transmitting optical path and a reflected light transmitting optical path for transmitting two or more optical signals having different wavelengths from each other, and an end of the outgoing light transmitting optical path of the two-core optical fiber. A collimator lens that transmits and converges the emitted optical signal, is disposed at the focal point of the collimator lens, transmits the collimator lens, transmits only the optical signal of a predetermined wavelength among the converged optical signals, and transmits light of other wavelengths. What is claimed is: 1. A multi-wavelength signal transmission device comprising: a bandpass filter that does not transmit an optical signal; and a light receiver that receives an optical signal transmitted through the bandpass filter, wherein the bandpass filter absorbs light at a wavelength position of an optical signal having a predetermined wavelength. Using a bandpass filter that shows the absorption spectrum with the shifted peak position of the band,
Further, as the collimator lens, the incident angle of the optical signal incident on the bandpass filter from the two-core optical fiber is such that the peak position of the light absorption band indicated by the bandpass filter at the incident angle matches the wavelength position of the optical signal of the predetermined wavelength. A multi-wavelength signal transmission device using a collimator lens having a focal length selected as described above. 2. A two-core optical fiber having an outgoing light transmitting optical path for transmitting two or more optical signals having different wavelengths from each other and a reflected light transmitting optical path, and an end of the outgoing light transmitting optical path of the two-core optical fiber. A collimator lens that transmits and converges the emitted optical signal, is disposed at the focal point of the collimator lens, transmits the collimator lens, transmits only the optical signal of a predetermined wavelength among the converged optical signals, and transmits light of other wavelengths. What is claimed is: 1. A multi-wavelength signal transmission device comprising: a bandpass filter that does not transmit an optical signal; and a light receiver that receives an optical signal transmitted through the bandpass filter, wherein the bandpass filter absorbs light at a wavelength position of an optical signal having a predetermined wavelength. Using a bandpass filter that shows the absorption spectrum with the shifted peak position of the band,
And, as the two-core optical fiber, the incident angle of the optical signal incident on the bandpass filter from the two-core optical fiber is such that the peak position of the light absorption band indicated by the bandpass filter at the incident angle coincides with the wavelength position of the optical signal of the predetermined wavelength. A multi-wavelength signal transmission apparatus using a two-core optical fiber in which the distance between the optical path for transmitting outgoing light and the optical path for transmitting reflected light is adjusted. 3. A two-core optical fiber having an outgoing light transmitting optical path for transmitting two or more optical signals having different wavelengths from each other and a reflected light transmitting optical path, and an end of the outgoing light transmitting optical path of the two-core optical fiber. A collimator lens that transmits and converges the emitted optical signal, is disposed at the focal point of the collimator lens, transmits the collimator lens, transmits only the optical signal of a predetermined wavelength among the converged optical signals, and transmits light of other wavelengths. What is claimed is: 1. A multi-wavelength signal transmission device comprising: a bandpass filter that does not transmit an optical signal; and a light receiver that receives an optical signal transmitted through the bandpass filter, wherein the bandpass filter absorbs light at a wavelength position of an optical signal having a predetermined wavelength. Using a bandpass filter that shows the absorption spectrum with the shifted peak position of the band,
Further, as the two-core optical fiber and the collimator lens, the incident angle of the optical signal incident on the bandpass filter from the two-core optical fiber is such that the peak position of the light absorption band indicated by the bandpass filter at the incident angle is an optical signal having a predetermined wavelength. Adjustment of the distance between the optical path for transmission light transmission and the optical path for reflected light transmission of the two-core optical fiber, and the determination of the focal length of the collimator lens so as to coincide with the wavelength position of the two-core optical fiber and the collimator lens A multi-wavelength signal transmission device characterized by using a combination of the above.