JP3573314B2 - Optical transceiver - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical transmitting / receiving device used for a single-core bidirectional optical communication line using an optical fiber.
[0002]
[Prior art]
As a bidirectional optical communication system using an optical fiber, there is a single-core bidirectional optical communication line system that transmits a bidirectional optical signal using a single optical fiber. In a single-core bidirectional optical communication line, two optical transceivers are connected by one optical fiber. As an optical transmission / reception device in a single-core bidirectional optical communication line, those shown in FIGS. 7 and 8 are considered. FIG. 7 is a side view showing a main part of an example of the optical transceiver, and FIG. 8 is a perspective view of a main part of the optical transceiver shown in FIG. This optical transceiver includes, for example, a semiconductor substrate 101 formed of a silicon semiconductor or a gallium arsenide semiconductor and having a photodiode 102 as a light receiving element formed on an upper surface thereof, a prism 103 bonded on the semiconductor substrate 101, and a semiconductor substrate 101. A rectangular parallelepiped semiconductor element 104 bonded on 101, a laser diode 105 as a light emitting element bonded on this semiconductor element 104, and a light emitted from the laser diode 105 and transmitted to another optical transceiver. the first optical signal L ₁ of, dissipate incident on the end face of the optical fiber 106 serving as a communication line, through an optical fiber 106 is transmitted from another optical transceiver, a second emitted from the end face of the optical fiber 106 and a lens 107 for directing the photodiode 102 of the optical signal L ₂ is focused.
[0003]
The prism 103 is disposed on the photodiode 102 on the semiconductor substrate 101. The semiconductor element 104 is disposed on the side of the prism 103, the laser diode 105 is arranged to emit a first optical signal L ₁ toward the prism 103 side. On the side of the prism 103 facing the laser diode 105, for example, a slope formed at an angle of 45 ° with respect to the upper surface of the semiconductor substrate 101 is formed, and a half mirror surface 103a is formed on the slope. As the optical fiber 106, for example, a large-diameter plastic optical fiber is used.
[0004]
In this configuration optical transceiver as is the laser diode 105 is driven by an unillustrated driving circuit, the first optical signal L ₁ from the laser diode 105 is emitted. The first optical signal _{L 1} is, for example, enters the half mirror surface 103a of the prism 103 at a numerical aperture of 0.1, where for example, about 50% of the amount of light is reflected, is incident on the lens 107. The first optical signal _{L 1} is condensed by the lens 107, and enters, for example, in the optical fiber 106 a numerical aperture of 0.1. The first numerical aperture of the optical signal L ₁ when emitted from the laser diode 105 is determined by the laser diode 105.
[0005]
On the other hand, the second optical signal L ₂ via the optical fiber 106 has been sent from another optical transceiver is emitted from the optical fiber 106, for example a numerical aperture of 0.3. The second optical signal _{L 2} is collected so that the lens 107, for example a numerical aperture of 0.3, incident on the half mirror surface 103a of the prism 103, for example, about 50% of the amount of light is transmitted through the photo The light enters the diode 102 and is converted into an electric signal by the photodiode 102. The second numerical aperture of the optical signal L ₂ at the time of exiting from the optical fiber 106 is determined by the optical fiber 106.
[0006]
[Problems to be solved by the invention]
In optical transmission and reception devices, miniaturization and high reliability are required. However, in the optical transmitting and receiving device as shown in FIGS. 7 and 8, since the lens 107 a second numerical aperture of the optical signal L ₂ after passing through a small, second optical signal L at the time of entering the photodiode 102 The light diameter (light beam diameter) of No. ₂ is large. In general, the photodiode, the more large size, since the operation speed parasitic capacitance is increased between the substrate is slow, and increase the size of the photodiode 102 in accordance with the second optical diameter of the optical signal L ₂ In this case, there is a problem that the size of the optical transmitting and receiving device is increased, and the operation speed of the photodiode 102 is reduced, thereby lowering the reliability. Further, in the optical transmitting and receiving device as shown in FIGS. 7 and 8, it is necessary to increase the dimensional prism 103 in accordance with the second optical diameter of the optical signal L _2, that the light transmitting and receiving apparatus is enlarged There is a problem.
[0007]
The present invention has been made in view of such a problem, and an object of the present invention is to provide an optical transmitting and receiving apparatus capable of ensuring miniaturization and ensuring high reliability by reducing the incident light diameter of an optical signal to a light receiving element. Is to do.
[0009]
請 Motomeko 1 optical transceiver according includes a light emitting element for emitting a first optical signal, a light receiving element for receiving the second optical signal, a first optical signal emitted from the light emitting element Is condensed and made incident on the end face of the optical fiber, and a second optical signal emitted from the end face of the optical fiber is condensed and guided to the light receiving element. An optical system for increasing the numerical aperture when the element enters the optical fiber than the numerical aperture when exiting the optical fiber. The optical system includes a first optical element that separates an optical path of a first optical signal emitted from a light emitting element from an optical path of a second optical signal incident on a light receiving element, and the optical path passing through the first optical element. A second optical element that condenses the first optical signal and guides it to the optical fiber, and condenses a second optical signal emitted from the end face of the optical fiber and guides the second optical signal to the first optical element. , The second optical element mainly includes a central portion through which the first optical signal passes and a peripheral portion through which the outer portion of the light beam in the second optical signal mainly passes, and the peripheral portion is smaller than the central portion. The focal length is configured to be short.
[0011]
In the optical transceiver of 請 Motomeko 1 wherein the first optical signal emitted from the light emitting element is condensed and enters the end face of the optical fiber by the optical system. Further, the second optical signal sent via the optical fiber is condensed by the optical system, guided to the light receiving element, and received by the light receiving element. The optical system increases the numerical aperture of the second light signal outside the light beam at the time of incidence on the light receiving element to be larger than the numerical aperture at the time of exiting the optical fiber. The diameter becomes smaller.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing the configuration of the optical transceiver according to the first embodiment of the present invention, and FIG. 2 is a perspective view of a main part of the optical transceiver shown in FIG. The optical transmitting and receiving apparatus according to the present embodiment is suitable for use in a home / premises communication network or the like using a large-diameter plastic fiber as a communication line. The optical transceiver includes a housing 11, and a connector 12 is provided in the housing 11. A connector 2 provided at an end of an optical fiber 1 serving as a communication line in a single-core bidirectional optical communication line is detachably connected to the connector portion 12. As the optical fiber 1, for example, a large-diameter plastic optical fiber is used.
[0013]
In the housing 11, a semiconductor substrate 21 made of, for example, a silicon semiconductor or a gallium arsenide semiconductor, a photodiode 22 formed as a light receiving element formed on the upper surface of the semiconductor substrate 21, and a first substrate A prism 23 as an optical element, a rectangular parallelepiped semiconductor element 24 bonded on the semiconductor substrate 21, a laser diode 25 as a light emitting element bonded on the semiconductor element 24, and light emitted from the laser diode 25. a first optical signal L ₁ to be transmitted to the other optical transceiver, is once made to converge at a predetermined position in front of the end face of the optical fiber 1, dissipate incident on the end face of the optical fiber 1, the optical fiber via one transmitted from another optical transceiver, photo by the second optical signal L ₂ emitted from the end face of the optical fiber 1 is focused diode A lens 27 as a second optical element for directing the de 22, the first optical signal L ₁ is disposed in a position to be converged, the exit position of the second optical signal L ₂ apparent optical fiber 1 A lens 28 as a third optical element that is farther from the lens 27 than the end face position is provided. The lenses 27 and 28 optimally couple the first optical signal L ₁ and the second optical signal L ₂ with the optical fiber 1.
[0014]
The prism 23 is disposed on the photodiode 22 on the semiconductor substrate 21. The semiconductor element 24 is disposed on the side of the prism 23, the laser diode 25 is arranged to emit a first optical signal L ₁ toward the prism 23 side. The prism 23 has, on the side facing the laser diode 25, a slope formed at an angle of, for example, 45 ° with respect to the upper surface of the semiconductor substrate 21, and a half mirror surface 23a is formed on the slope.
[0015]
The above components in the housing 11 are integrated by a package 13 and a lens support frame 14. That is, the semiconductor substrate 21 is fixed to the bottom in the package 13, and the lens 27 is attached to the upper surface of the package 13. The lens 28 is supported by a lens support frame 14 fixed to the upper surface of the package 13 so as to surround the lens 27. The package 13 is fixed to an inner surface of the housing 11.
[0016]
Next, the operation of the optical transceiver according to the present embodiment will be described. The laser diode 25 is driven by an unillustrated driving circuit, and emits a first optical signal L _1. The first optical signal L ₁ is, for example, enters the half mirror surface 23a of the prism 23 with a numerical aperture of 0.1, where for example, about 50% of the amount of light is reflected, is incident on the lens 27. The first optical signal L ₁ is condensed by the lens 27 at, for example, a numerical aperture of 0.1, and once converges at a predetermined position before the end face of the optical fiber 1, that is, at the center position of the lens 28, Incident on the end face. Incidentally, the position of the end face of the optical fiber 1, incident light diameter of the first optical signal L ₁ is set so as not to exceed the diameter of the core of the optical fiber 1. The first numerical aperture of the optical signal L ₁ when emitted from the laser diode 25 is determined by the laser diode 25.
[0017]
On the other hand, the second optical signal L ₂ via the optical fiber 1 has been sent from another optical transceiver is emitted from the end face of the optical fiber 1, for example a numerical aperture of 0.3. The second optical signal L ₂ is first focused by a lens 28, is condensed further by the lens 27, is incident on the half mirror surface 23a of the prism 23, for example, about 50% of the amount of light is transmitted through the photo The light enters the diode 22 and is converted into an electric signal by the photodiode 22. The second numerical aperture of the optical signal L ₂ at the time of exiting from the optical fiber 1 is determined by the optical fiber 1.
[0018]
In the optical transmitting and receiving apparatus according to this embodiment, the position of the first position of the laser diode 25 is emitting position of the optical signal L _1, a first optical signal L ₁ of the convergence position at which the lens 28, the lens 27 Has a target positional relationship with respect to. That is, assuming that the position of the laser diode 25 is an object point with respect to the lens 27 and the position of the lens 28 is an image point with respect to the lens 27, the distance from the center of the lens 27 to the object point is equal to the distance from the center of the lens 27 to the image point. Has become. Accordingly, the first lens 27 aperture before and after the incident optical signal L ₁ are both for example 0.1, are equal. On the other hand, the position of the end face of the optical fiber 1 which is a second output position of the optical signal L ₂ is slightly far made by the lens 27 than the position of the first optical signal L ₁ of the convergence position at which the lens 28 I have. Further, by the action of the lens 28, the output position of the second optical signal L ₂ apparently has kept away from the lens 27 than the position of the end face of the optical fiber 1. Accordingly, the object point of the exit position of the second optical signal L ₂ apparent with respect to the lens 27, the second converging position of the light signal L ₂ of the lens 27 after passing through when the image point from the center of the lens 27 to the image point Is shorter than the distance from the center of the lens 27 to the object point, and the second optical signal L ₂ emitted from the optical fiber 1 with the numerical aperture of 0.3 is converted by the lens 27 into the numerical aperture of 0.3 + α ( α is a positive number). Here, α is an effect due to the apparent emission position of the _second optical signal L ₂ being kept away from the lens 27. As a result, the second optical diameter of the optical signal L ₂ on the photodiode 22 is smaller than the light receiving device shown in FIGS.
[0019]
For example, the alpha = 0.1, and a second opening area of the light signal L ₂ on the photodiode 22 in the case where the same configuration as that of FIG. 7 and 8 without providing the lens 28, Fig. 1 provided with a lens 28 and the ratio of the second opening area of the light signal L ₂ on the photodiode 22 when configured as shown in FIG. 2, 9: 1 If set, according to the optical transmitting and receiving apparatus according to this embodiment For example, the second optical signal L ₂ is condensed by the lens 27 with a numerical aperture of 0.4, and the light diameter of the second optical signal L ₂ on the photodiode 22 is the light diameter shown in FIGS. It is reduced to {(1/9)} 33% compared to the transmitting / receiving device. The second optical signal L ₂ is not always necessary to converge on the photodiode 22 may be once converged before reaching the photodiode 22, and reaches the photodiode 22 without converging Is also good.
[0020]
The first optical signal L _1, since converge at the center of the lens 28 passes through the lens 28, when viewed as a central portion of the lens 28 is almost flat, the first optical signal L ₁ is Since the light passes through the lens 28 as it is, the first optical signal L ₁ is not affected by the lens 28. Incidentally, either flat machined central portion of the lens 28, I open the minute pores in the central portion of the lens 28, the effect on the first optical signal L ₁ of the lens 28 can be removed completely.
[0021]
As described above, according to the optical transmitting and receiving apparatus according to the present embodiment, while keeping the incident light diameter of the first to the optical fiber 1 of the optical signal L ₁ to a suitable size, the second optical signal L Only the diameter of light incident on the _second photodiode 22 can be reduced to, for example, 33%. As a result, the photodiode 22 and the prism 23 can be reduced in size, and the operating speed of the photodiode 22 can be increased due to the reduction in the size of the photodiode 22, so that the optical transceiver can be reduced in size and high reliability can be ensured. Become.
[0022]
FIG. 3 is an explanatory diagram illustrating a main part of a first modification of the optical transceiver according to the present embodiment. 1 and 2, the photodiode 22, the prism 23, and the laser diode 25 are integrated on a single semiconductor substrate 21 to reduce the size of the device. May be separated from each other. The first modification shown in FIG. 3 is an example in which a half mirror 31 is provided instead of the prism 23, and the photodiode 22, the laser diode 25, and the half mirror 31 are provided separately without being integrated. The operation of the first modification is the same as that of the first embodiment.
[0023]
FIG. 4 is an explanatory diagram illustrating a main part of a second modification of the optical transceiver according to the present embodiment. The second modification is an example in which the positions of the photodiode 22 and the laser diode 25 in the first modification are interchanged. In the second modification, the first optical signal L ₁ emitted from the laser diode 25 is transmitted through the half mirror 31, for example, approximately 50% of the light amount, enters the lens 27, and the second optical signal L 1 Reference numeral ₂ denotes a half mirror 31 which reflects, for example, approximately 50% of the light amount and enters the photodiode 22.
[0024]
FIG. 5 is a cross-sectional view illustrating a configuration of the optical transceiver according to the second embodiment of the present invention. In the optical transmitting and receiving apparatus according to the present embodiment, lens 28 is disposed closer to lens 27 than the convergence position of _first optical signal L1. In this case, the lens 28, in cooperation with the lens 27, is once made to converge at a predetermined position in front of the first optical signal L ₁ the end face of the optical fiber 1, dissipate incident on the end face of the optical fiber 1, a function away from the first embodiment similarly to the second optical signal L ₂ of the lens 27 than the position of the end face of the emitting position of the apparent optical fiber 1.
[0025]
In the optical transmitting and receiving apparatus according to this embodiment, the first optical signal L ₁ is approximately 50% of the half-mirror surface 23a of the prism 23 for example light quantity is reflected is condensed by the lens 27 and the lens 28, the optical fiber After converging once at a predetermined position before the end face of the optical fiber 1, the light is incident on the end face of the optical fiber 1. As in the first embodiment, the position of the end face of the optical fiber 1, incident light diameter of the first optical signal L ₁ is set so as not to exceed the diameter of the core of the optical fiber 1. On the other hand, the second optical signal L ₂ transmitted from another optical transceiver through the optical fiber 1 is emitted from the end face of the optical fiber 1 is condensed by the lens 28 and lens 27, the half prism 23 For example, approximately 50% of the light amount is transmitted through the mirror surface 23a and enters the photodiode 22.
[0026]
Also in this embodiment, the object point of the exit position of the second optical signal L ₂ apparent with respect to the lens 27, when the second convergence position of the optical signal L ₂ of the lens 27 after passing through the image point of the lens 27 The distance from the center to the image point is shorter than the distance from the center of the lens 27 to the object point, and the second optical signal L ₂ emitted from the optical fiber 1 at, for example, a numerical aperture of 0.3 is converted by the lens 27. The light is condensed at a numerical aperture of 0.3 + α (α is a positive number). As a result, the second optical diameter of the optical signal L ₂ on the photodiode 22 is smaller than the light receiving device shown in FIGS. Other configurations, operations, and effects of the present embodiment are the same as those of the first embodiment.
[0027]
FIG. 6 is a cross-sectional view illustrating a configuration of an optical transceiver according to a third embodiment of the present invention. In the optical transmitting and receiving apparatus according to the present embodiment, the lens 28 and the lens support frame 14 in the first embodiment are not provided, and the lens 41 is provided instead of the lens 27 in the first embodiment. ing. The lens 41 is mainly includes a central portion 41a in which the first optical signal L ₁ passes through mainly a peripheral portion 41b of the outer portion of the second beam in the optical signal L ₂ passes, the peripheral portion 41b The focal length is designed to be shorter than that of the central portion 41a. When this lens 41 is compared with the lens 107 in the optical transceiver shown in FIGS. 7 and 8, the focal length of the central portion 41a is the same as that of the lens 107, but the focal length of the peripheral portion 41b is the focal length of the lens 107. Is shorter than
[0028]
In the optical transmitting and receiving apparatus according to the present embodiment, for example, approximately 50% of the light amount of the first optical signal L ₁ emitted from the laser diode 25 at a numerical aperture of 0.1 is reflected by the half mirror surface 23 a of the prism 23. Then, the light enters the central portion 41 a of the lens 27, is collected, and is incident on the end face of the optical fiber 1 so as to converge substantially at the end face position of the optical fiber 1. On the other hand, the second optical signal L ₂ via the optical fiber 1 has been sent from another optical transceiver is emitted at the end face than the example numerical aperture 0.3 of the optical fiber 1, the central portion 41a and the lens 27 The light enters the peripheral portion 41b. Here, among the second optical signal L _2, the outer portion of the light beam passing through a short peripheral portion 41b of the focal length in the lens 41 is focused at a greater numerical aperture than 0.3, a half mirror prism 23 For example, approximately 50% of the light amount is transmitted through the surface 23a and enters the photodiode 22. Therefore, the light diameter of the photodiode 22 at the incident of the outer portion of the second beam in the optical signal L ₂ is smaller than that of the optical transmitting and receiving apparatus shown in FIGS. The portion that passes through the second central portion 41a of the lens 41 of the optical signal L ₂ is, for example, is condensed with a numerical aperture of 0.3 enters the photodiode 22, but the second optical signal L ₂ Since the light diameter of the portion passing through the central portion 41a of the lens 41 is originally smaller than the light diameter of the entire _second optical signal L2, the light diameter at the time of incidence on the photodiode 22 is also shown in FIGS. The size is smaller than in the case of the optical transmitting / receiving device shown.
[0029]
Thus, according to the optical transmitting and receiving apparatus according to the present embodiment, while keeping the incident light diameter of the first to the optical fiber 1 of the optical signal L ₁ to a suitable size, the second optical signal L ₂ Only the diameter of light incident on the photodiode 22 can be reduced. Note that, in the present embodiment, instead of the lens 41, a lens having a function equivalent to the lens 41 is used by joining a small-diameter concave lens to the center of a lens having a single focal length. Alternatively, a hologram formed to have the same function as the lens 41 may be used. Other configurations, operations, and effects of the present embodiment are the same as those of the first embodiment.
[0030]
Note that the present invention is not limited to the above embodiments. For example, a light emitting diode (LED) may be used instead of a laser diode as a light emitting element. Further, the present invention can be applied to all single-core bidirectional optical communication lines, such as outside-home / public communication networks using large-diameter optical fibers other than plastic optical fibers as communication lines.
[0032]
According to the optical transmitter-receiver according to 請 Motomeko 1, second light emitted from the end face of and optical fiber to be incident by condensing a first optical signal emitted from the light-emitting element on the end face of the optical fiber Since the optical system condenses the signal and guides it to the light receiving element, and for the outer part of the light beam in the second optical signal, the optical system has a numerical aperture at the time of incidence of the light receiving element larger than the numerical aperture at the time of exiting the optical fiber. The diameter of the incident light of the second optical signal on the light receiving element is reduced, and as a result, the light receiving element and the optical members constituting the optical system can be reduced in size, and the optical transceiver can be reduced in size and high reliability can be secured. This has the effect of becoming
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of an optical transceiver according to a first embodiment of the present invention.
FIG. 2 is a perspective view of a main part of the optical transceiver shown in FIG.
FIG. 3 is an explanatory diagram showing a main part of a first modified example of the optical transceiver according to the first embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a main part of a second modified example of the optical transceiver according to the first embodiment of the present invention.
FIG. 5 is a cross-sectional view illustrating a configuration of an optical transceiver according to a second embodiment of the present invention.
FIG. 6 is a cross-sectional view illustrating a configuration of an optical transceiver according to a third embodiment of the present invention.
FIG. 7 is a side view showing a main part of an example of the optical transceiver.
FIG. 8 is a perspective view of a main part of the optical transceiver shown in FIG. 7;
[Explanation of symbols]
1 ... optical fiber, 21 ... semiconductor substrate, 22 ... photodiode, 23 ... prisms, 23a ... half mirror surface, 25 ... laser diode, 27 ... lens, 28 ... lens, L 1 _... first optical signal, _{L 2} ... Second optical signal

Claims (1)

A first optical signal to be transmitted is connected to an optical fiber serving as a communication line in a single-core bidirectional optical communication line, and a first optical signal to be transmitted is made incident on the optical fiber, and a second optical signal transmitted through the optical fiber is received. An optical transmitting and receiving device,
A light emitting element for emitting the first optical signal;
A light receiving element for receiving the second optical signal;
A first optical signal emitted from the light emitting element is collected and made incident on the end face of the optical fiber, and a second optical signal emitted from the end face of the optical fiber is collected and guided to the light receiving element. And an optical system for increasing the numerical aperture at the time of incidence of the light-receiving element than the numerical aperture at the time of emission of the optical fiber, for an outer portion of the light beam in the second optical signal ,
A first optical element for separating an optical path of a first optical signal emitted from the light emitting element from an optical path of a second optical signal incident on the light receiving element; and the first optical element A second optical signal that condenses the first optical signal passing through the optical fiber and guides the optical signal to the optical fiber, and condenses a second optical signal emitted from the end face of the optical fiber and guides the second optical signal to the first optical element. A second optical element, wherein the second optical element mainly includes a central portion through which the first optical signal passes and a peripheral portion through which an outer portion of the light beam mainly in the second optical signal passes; Wherein the focal length is shorter than that of the central part .

Images