JP4225152B2 - Optical power monitor device - Google Patents

Description

  The present invention relates to an optical power monitoring device that monitors the power of light input to an input port.

  An optical power monitoring device described in Non-Patent Document 1 includes a substrate having a groove formed on the surface, an optical fiber disposed in the groove, and an optical filter disposed obliquely in the middle of the optical fiber in the groove. And a light receiving element that is disposed on the substrate and monitors the power of light of a specific wavelength reflected by the optical filter. Before and after the optical filter, the optical fiber is cut obliquely according to the inclination of the optical filter.

In this optical power monitor device, the light input to one end (input port) of the optical fiber propagates through the optical fiber and reaches the optical filter, and the light of a specific wavelength among the light is reflected by the optical filter and is used as a substrate. The light exits above the substrate and the light exits above the substrate is monitored for power by the light receiving element. The light transmitted through the optical filter further propagates through the optical fiber and is output from the other end (output port) of the optical fiber.
T. Uno, et al., "Novel 1.3 / 1.55 μm dual-wavelength receiver having embedded fiber circuit for optical subscriber systems", OFC'96 Technical Digest, TuJ5 (1996)

  In the above conventional optical power monitoring device, the light reflected by the optical filter passes through the cladding region of the optical fiber, and further passes through the medium between the optical fiber and the light receiving element to reach the light receiving element. To do. Therefore, the light receiving sensitivity of the light receiving element is affected by the scattering of the substance on the optical path until the light reflected by the optical filter reaches the light receiving element and the temperature characteristic of the refractive index. In addition, since the light receiving element is fixed on the substrate with an adhesive, the position of the light receiving element varies depending on the temperature due to the linear expansion coefficient of the adhesive and the nonuniformity of the coating amount, and the light receiving sensitivity of the light receiving element is May be affected. Thus, in the above conventional optical power monitor device, the temperature dependence of the light receiving sensitivity is large.

  Further, in the above conventional optical power monitoring device, there is an optical interface on the optical path until the light reflected by the optical filter reaches the light receiving element, and the polarization is caused by the light passing through the interface. Dependency loss occurs. Also, if one side of the interface is air, the polarization dependent loss is even greater.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical power monitoring device capable of reducing the temperature dependence and polarization dependence of light receiving sensitivity.

An optical power monitoring apparatus according to the present invention is an optical power monitoring apparatus that monitors the power of light input to an input port, and (1) a first lens that collects light input to the input port, and a first lens. An optical filter provided at a light condensing position for transmitting at least part of the light input to the input port and reflecting other light, and collecting the light reflected by the optical filter and outputting it from the output port. A transparent member having two lenses formed on the surface, and (2) a light receiving element that monitors the power of light that has passed through an optical filter formed on the surface of the transparent member and has exited the transparent member. It is characterized by providing. Further, the first lens and the second lens are formed on the first surface of the transparent member, and the optical filter is formed on another second surface parallel to the first surface of the transparent member.

  In this optical power monitor device, a first lens, a second lens, and an optical filter are formed on the surface of a transparent member. The light input to the input port is converged by the first lens, travels through the transparent member, and is collected on the optical filter. A part of the light collected on the optical filter passes through the optical filter, and the other light is reflected by the optical filter. The light reflected by the optical filter travels through the transparent member, enters the second lens, is converged by the second lens, and is output from the output port. On the other hand, the light that has passed through the optical filter exits the transparent member, enters the light receiving element through the space between the transparent member and the light receiving element, and the power is monitored by the light receiving element.

  The optical power monitoring device according to the present invention preferably includes azimuth fixing means for fixing a relative azimuth relationship among the input port, the output port, the transparent member, and the light receiving element. The optical power monitoring device according to the present invention fixes the distance between the input port and the transparent member, the distance between the output port and the transparent member, and the distance between the transparent member and the light receiving element. It is preferable to provide a distance fixing means. In these cases, the optical power monitor device can be easily manufactured.

  In the optical power monitoring device according to the present invention, the linear expansion coefficient of the transparent member can cause the condensing position on the transparent member side of each of the first lens and the second lens to be present on the optical filter even when the temperature fluctuates. It is suitable. In this case, the temperature dependence of the efficiency of optical coupling from the input port to the output port can be reduced.

  In the optical power monitoring apparatus according to the present invention, it is preferable that the optical filter branches the light of a specific wavelength. In this case, it is convenient to monitor the power of the light of the specific wavelength.

  In the optical power monitoring device according to the present invention, it is preferable that the polarization dependency of the transmittance of the optical filter at a specific wavelength is 5% or less. In this case, the polarization state of light input to the input port Regardless of this, the power of light of a specific wavelength can be monitored stably.

  In the optical power monitoring device according to the present invention, it is preferable that the wavelength dependency of the transmittance of the optical filter is 5% or less. In this case, even if the wavelength of light input to the input port varies slightly. The power of light of a specific wavelength can be monitored stably.

  In the optical power monitoring device according to the present invention, a plurality of sets of input ports, output ports, first lenses, second lenses and light receiving elements are provided, and the plurality of sets of first lenses and second lenses are provided on the surface of one transparent member. It is preferable that they are formed in an array. In this case, the power of light input to each input port is monitored in each of the plurality of sets. In addition, since the plurality of sets of the first lens and the second lens are arranged on the surface of one transparent member, the optical power monitoring device can be easily manufactured.

  The optical power monitoring device according to the present invention preferably further includes first position fixing means for fixing the relative positional relationship between each of the plurality of sets of input ports and output ports. The optical power monitoring device according to the present invention preferably further includes a second position fixing means for fixing the relative positional relationship between each of the plurality of light receiving elements. In these cases, the optical power monitor device can be more easily manufactured.

  In the optical power monitoring apparatus according to the present invention, an optical filter may be provided for each of the plurality of sets, but the optical filter is provided in common for the plurality of sets of the first lens and the second lens. In the latter case, an optical filter can be easily formed on the surface of the transparent member.

  According to the present invention, the temperature dependency and polarization dependency of the light receiving sensitivity can be reduced.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In each figure, an xyz rectangular coordinate system is shown for convenience of explanation.

FIG. 1 is a perspective view of an optical power monitor device 1 according to the present embodiment. The optical power monitoring device 1 shown in this figure includes an optical fiber array section 10, a transparent member 20, a photodiode array section 30, guide pins 41 to 44, and spacers 51 to 58. In this figure, the spacers 53 and 57 do not appear. The optical power monitor device 1 is used in conjunction with optical fibers 91 ₁ to 91 _4, 92 ₁ to 92 _4.

  Each of the optical fiber array unit 10, the transparent member 20, and the photodiode array unit 30 has a substantially rectangular parallelepiped shape, and has through holes through which four guide pins 41 to 44 penetrate in parallel with each other at four corners. Yes. A direction in which each of the rod-shaped guide pins 41 to 44 extends is a z-axis direction. Each of the optical fiber array unit 10, the transparent member 20, and the photodiode array unit 30 is arranged such that each side is parallel to any of the x-axis, y-axis, and z-axis.

  Four spacers 51 to 54 are provided between the optical fiber array unit 10 and the transparent member 20. Each of the four spacers 51 to 54 has a pipe shape and has the same length. The spacer 51 is penetrated by the guide pin 41, the spacer 52 is penetrated by the guide pin 42, the spacer 53 is penetrated by the guide pin 43, and the spacer 54 is penetrated by the guide pin 44.

  Four spacers 55 to 58 are provided between the transparent member 20 and the photodiode array unit 30. Each of the four spacers 55 to 58 has a pipe shape and has the same length. The guide pin 41 penetrates the spacer 55, the guide pin 42 penetrates the spacer 56, the guide pin 43 penetrates the spacer 57, and the guide pin 44 penetrates the spacer 58.

The optical fiber array unit 10 has a through hole for arranging eight optical fibers 91 ₁ to 91 _4, 92 ₁ to 92 ₄ 2D. Eight optical fibers 91 ₁ to 91 _4, 92 parts held by the inner optical fiber array unit 10 of _{1-92 4} is parallel to the z-axis direction, parallel optical fibers 91 ₁ to 91 ₄ in the xz plane such is arranged on the surface, the optical fiber 92 ₁ to 92 ₄ are arranged on a plane parallel to the xz plane, the optical fiber 91 ₁ and the optical fiber 92 ₁ is arranged on a plane parallel to the yz plane, the optical fiber 91 ₂ and the optical fiber 92 ₂ are arranged on a plane parallel to the yz plane, the optical fiber 91 ₃ and the optical fiber 92 ₃ are arranged on a plane parallel to the yz plane, and the optical fiber 91 ₄ and the optical fiber 92 ₄ are arranged. Are arranged on a plane parallel to the yz plane. The optical fiber array unit 10, on a surface facing the transparent member 20, the optical fiber 91 ₁ to 91 _4, 92 ₁ to 92 ₄ each of the end faces are located.

The transparent member 20 is made of a transparent material from the end face of the optical fiber 91 ₁ to 91 _4, 92 ₁ to 92 ₄ to light incidence and emission (e.g. quartz glass). The transparent member 20 has lenses 21 _{1 to} 21 ₄ and 22 _{1 to} 22 ₄ formed on the surface facing the optical fiber array section 10. Each of the lenses 21 _{1 to} 21 ₄ and 22 _{1 to} 22 ₄ is formed by molding the surface of the transparent member 20, has the same shape, and has the same optical characteristics. In this figure, the lenses 21 ₄ and 22 _{1 to} 22 ₃ do not appear. The lens 21 ₁ on the transparent member 20 is at a position substantially opposite to the end face of the optical fiber 91 ₁ , and the lens 21 ₂ on the transparent member 20 is at a position substantially opposite to the end face of the optical fiber 91 ₂ , the lens 21 ₃ in a position substantially facing the end face of the optical fiber 91 _3, lens 21 ₄ of the transparent member 20 is located at a position substantially facing the end face of the optical fiber 91 _4, the lens 22 ₁ on the transparent member 20 Is at a position substantially opposite to the end face of the optical fiber 92 ₁ , the lens 22 ₂ on the transparent member 20 is at a position substantially opposite to the end face of the optical fiber 92 ₂ , and the lens 22 ₃ on the transparent member 20 is at the optical fiber 92. located substantially opposite positions on the end surface of _3, also, the lens 22 ₄ of the transparent member 20 is positioned substantially facing the end face of the optical fiber 92 _4.

  In the transparent member 20, an optical filter 23 is formed on a surface facing the photodiode array unit 30. The optical filter 23 transmits at least part of the input light and reflects other light, and is made of, for example, a dielectric multilayer film. The optical filter 23 preferably splits power of light of a specific wavelength. For example, it is preferable that the transmittance is 10% and the reflectance is 90% at the specific wavelength. In addition, it is preferable that the polarization dependency of the transmittance of the optical filter 23 at a specific wavelength is 5% or less. In this case, the transmission is stable regardless of the polarization state of the light input to the input port. The power of light of a specific wavelength can be monitored. Further, it is preferable that the wavelength dependency of the transmittance of the optical filter 23 is 5% or less. In this case, even if the wavelength of the light input to the input port slightly varies, the power of the light is stabilized. Can be monitored.

Photodiode array 30 has four photodiodes 31 ₁ to 31 ₄ as a light receiving element on a surface facing the transparent member 20. In this drawing it does not appear photodiode 31 _{2-31 4.} Four photodiodes 31 ₁ to 31 ₄ are arranged in the x-axis direction. The photodiode 31 ₁ receives light that has passed through the lens 21 ₁ and the optical filter 23 out of light emitted from the end face of the optical fiber 91 ₁ , and monitors the power of the light. The photodiode 31 ₂ receives the light that has passed through the lens 21 ₂ and the optical filter 23 out of the light emitted from the end face of the optical fiber 91 ₂ , and monitors the power of the light. The photodiode 31 ₃ receives light that has passed through the lens 21 ₃ and the optical filter 23 out of light emitted from the end face of the optical fiber 91 ₃ , and monitors the power of the light. Further, the photodiode 31 ₄ receives the light passing through the lens 21 ₄ and the optical filter 23 of the light emitted from the end face of the optical fiber 91 _4, monitoring the power of the light.

FIG. 2 is a perspective view of the transparent member 20 included in the optical power monitor device 1 according to the present embodiment. As shown in this figure, the transparent member 20 has lenses 21 _{1 to} 21 ₄ and 22 _{1 to} 22 ₄ formed on the surface facing the optical fiber array section 10. The lenses 21 _{1 to} 21 ₄ are arranged in the x-axis direction, and the lenses 22 _{1 to} 22 ₄ are also arranged in the x-axis direction.

FIG. 3 is a perspective view of the photodiode array unit 30 included in the optical power monitor device 1 according to the present embodiment. As shown in this figure, the photodiode array section 30 has four photodiodes 31 _{1 to} 31 ₄ on the surface facing the transparent member 20. Photodiode 31 _{1-31 4} are arranged in the x-axis direction.

Figure 4 is a xz cross-sectional view of an optical power monitor device 1 according to the present embodiment, and shows a cross section when cut by a plane including the optical fiber 91 ₁ to 91 ₄ each optical axis. FIG. 5 is a yz cross-sectional view of the optical power monitoring device 1 according to the present embodiment, showing a cross section when cut along a plane including the optical axes of the optical fibers 91 ₁ and 92 ₁ . In these drawings, the center of light entering and exiting from the end face of each optical fiber is indicated by a one-dot chain line. In the following description, n represents an integer of 1 to 4.

The optical axes of the lenses 21 _n and 22 _n formed on one surface of the transparent member 20 are parallel to the optical axes of the optical fibers 91 _n and 92 _n . However, the optical axes of the lens 21 _n and the optical fiber 91 _n are not on a common straight line but are shifted in the y-axis direction. Further, the optical axes of the lens 22 _n and the optical fiber 92 _n are not on a common straight line but are shifted in the y-axis direction.

The lens 21 _n receives light output as divergent light from the end face (input port) of the optical fiber 91 _n located on the surface of the optical fiber array unit 10, and condenses the light on the optical filter 23. The optical filter 23 formed on the other surface of the transparent member 20 inputs the light that has been collected and reached by the lens 21 _n , transmits at least part of the light, and transmits the other light to the lens 22. _Reflect to _n . The lens 22 _n receives and collects the light that has been reflected by the optical filter 23 and collects the light, and inputs the light to the end face (output port) of the optical fiber 92 _n located on the surface of the optical fiber array unit 10. The photodiode 31 _n receives a portion of the light that has passed through the optical filter 23 and has exited the transparent member 20, and monitors the power of the light.

Next, the operation of the optical power monitor device 1 according to this embodiment will be described. Light optical fiber 21 _n has been guided is output from the end face of the optical fiber 21 _n, input to the input port of the optical power monitor device 1. Light outputted from the end face of the optical fiber 21 _n is input to the lens 21 _n proceed parallel to the z-axis while diverging, it is converging by the lens 21 _n. The light converged by the lens 21 _n travels through the transparent member 20 in a direction that forms an angle with respect to the z-axis direction, and is condensed on the optical filter 23. A part of the light collected on the optical filter 23 passes through the optical filter 23, and the remaining light is reflected by the optical filter 23.

The light reflected by the optical filter 23 is input to the lens 22 _n advances through the transparent member 20 in the direction forming an angle to the z-axis direction while diverging, it is converging by the lens 22 _n. The light converged by the lens 22 _n travels parallel to the z-axis, is condensed on the end face of the optical fiber 92 _n , is output from the output port of the optical power monitor device 1 and is input to the end face of the optical fiber 92 _n . On the other hand, the light that has passed through the optical filter 23 exits from the transparent member 20 and enters the photodiode 31 _n through the space between the transparent member 20 and the photodiode array section 30, and is powered by the photodiode 31 _n. Is monitored.

As described above, in the optical power monitoring device 1 according to the present embodiment, the lens 21 _{n in} the optical path from the end face (input port) of the optical fiber 91 _n to the optical filter 23 (hereinafter referred to as “first optical path”). Constitutes a condensing optical system, and the lens 22 _n constitutes a condensing optical system in the optical path from the optical filter 23 to the end face (output port) of the optical fiber 92 _n (hereinafter referred to as “second optical path”). ing. There is no interface in the optical path from the optical filter 23 to the photodiode 31 _n (hereinafter referred to as “third optical path”). Further, an adhesive or other medium that scatters light is not provided in each of the first optical path, the second optical path, and the third optical path. Therefore, the optical power monitoring device 1 according to the present embodiment can reduce the temperature dependency and polarization dependency of the light receiving sensitivity.

The guide pins 41 to 44, the end face of the optical fiber 91 ₁ to 91 ₄ (input port), the end face of the optical fiber 92 ₁ to 92 ₄ (output port), the transparent member 20 and the photodiode 31 _{1-31 4} each It fixes the relative azimuth relationship between them and acts as an azimuth fixing means. The spacer 51 to 58, between the end faces of the optical fibers 91 ₁ to 91 ₄ (input port) and the transparent member 20 a distance, between the end face of the optical fiber 92 ₁ to 92 ₄ (output port) and the transparent member 20 distance, and the distance between the transparent member 20 and the photodiode 31 _{1-31 4,} which fixes the respective acts as a distance fixing means. The optical fiber array unit 10 functions as first position fixing means for fixing the relative positional relationship between each of the four sets of input ports and output ports. The photodiode array section 30 functions as second position fixing means for fixing the relative positional relationship between the _four photodiode photodiodes 31 _{1 to} 31 ₄ . The optical power monitoring device 1 includes such azimuth fixing means, distance fixing means, first position fixing means, or second position fixing means, so that positioning of each component and adjustment of the optical axis are not required during assembly. It becomes easy and a high-precision thing can be produced easily.

Further, the linear expansion coefficient of the transparent member 20 is such that the condensing position on the transparent member 20 side of each of the lens 21 _n and the lens 22 _n can exist on the optical filter 23 even when the temperature varies. Is preferred. That is, when there is a temperature variation, the lens 21 _n and the lens 22 _n and the amount of z-axis direction of the fluctuation of the focusing position of each of the transparent member 20 side, of the z-axis direction of the transparent member 20 thermal expansion or contraction It is preferable that the amounts of the two are substantially equal to each other.

The focal length of each of the lens 21 _n and the lens 22 _{n on} the transparent member 20 side (the distance between the surface on which each lens is formed and the condensing position on the transparent member 20 side) f is the refractive index n of the transparent member 20. And a function having the curvature β of the lens surface of each lens as a variable. The refractive index n of the transparent member 20 is expressed by a function having the temperature T as a variable. The curvature β of the lens surface of each lens is also expressed by a function having the temperature T as a variable. Further, the thickness of the transparent member 20 in the z-axis direction (the distance between the surface on which each lens is formed and the optical filter 23) is also expressed by a function having the temperature T as a variable.

When the linear expansion coefficient of the transparent member 20 is α and the thickness of the transparent member 20 in the z-axis direction at the reference temperature T ₀ is d ₀ , any temperature within the operating temperature range (for example, −20 ° C. to + 80 ° C.). At T (= T ₀ + ΔT), it is preferable that the focal length of the lens 21 _n and the lens 22 _{n on} the transparent member 20 side and the thickness of the transparent member 20 in the z-axis direction are substantially equal to each other. Between each parameter, f (β (T), n (T)) = d ₀ (1 + αΔT) (1)
It is preferable that the following relational expression holds. By using the transparent member 20 made of a material satisfying such conditions, the optical power monitoring device 1 according to the present embodiment can be used from the end face (input port) of the optical fiber 91 _{n to} the end face (output port) of the optical fiber 92 _n. The temperature dependence of the efficiency of optical coupling to can be reduced.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the optical power monitor device 1 according to the above embodiment, the optical filter 23 is formed on the surface of the transparent member 20 in common for the four channels, but the optical filter may be provided for each of the four channels. Good. In the former case, the optical filter 23 can be easily formed on the surface of the transparent member 20. On the other hand, in the latter case, the wavelength of light to be monitored can be easily made different for each channel by making the transmission wavelength of the optical filter different for each channel. Moreover, although the optical power monitoring apparatus 1 according to the above embodiment has four channels, in the present invention, the number of channels is arbitrary.

1 is a perspective view of an optical power monitor device 1 according to the present embodiment. It is a perspective view of the transparent member 20 contained in the optical power monitor apparatus 1 which concerns on this embodiment. FIG. 3 is a perspective view of a photodiode array unit 30 included in the optical power monitor device 1 according to the present embodiment. It is xz sectional drawing of the optical power monitor apparatus 1 which concerns on this embodiment. It is yz sectional drawing of the optical power monitor apparatus 1 which concerns on this embodiment.

Explanation of symbols

1 ... optical power monitor device, 10 ... optical fiber array unit, 20 ... transparent member, 21 ₁ to 21 _4, 22 ₁ to 22 ₄ ... lens, 23 ... optical filter, 30 ... photodiode array unit, 31 _{1-31 4} ... Photodiode, 41 to 44... Guide pin, 51 to 58. Spacer, 91 _{1 to} 91 ₄ , 92 _{1 to} 92 ₄ .

Claims (11)

An optical power monitoring device for monitoring the power of light input to an input port,
A first lens that condenses light input to the input port, and light that is provided at a light condensing position of the first lens and transmits at least part of the light input to the input port and reflects other light. A transparent member formed on the surface of a filter and a second lens that collects the light reflected by the optical filter and outputs the light from the output port;
A light receiving element that monitors the power of light that has passed through the optical filter formed on the surface of the transparent member and has exited the transparent member;
Bei to give a,
The first lens and the second lens are formed on a first surface of the transparent member;
The optical filter is formed on another second surface parallel to the first surface of the transparent member;
An optical power monitor device characterized by that.
  2. The optical power monitoring apparatus according to claim 1, further comprising azimuth fixing means for fixing a relative azimuth relationship among the input port, the output port, the transparent member, and the light receiving element.   Distance fixing means for fixing the distance between the input port and the transparent member, the distance between the output port and the transparent member, and the distance between the transparent member and the light receiving element are provided. The optical power monitoring apparatus according to claim 1.   The linear expansion coefficient of the transparent member can cause the condensing position on the transparent member side of each of the first lens and the second lens to be present on the optical filter even when the temperature varies. The optical power monitor apparatus according to claim 1.   The optical power monitoring apparatus according to claim 1, wherein the optical filter branches power of light having a specific wavelength.   2. The optical power monitor device according to claim 1, wherein the polarization dependency of the transmittance of the optical filter at the specific wavelength is 5% or less.   2. The optical power monitor device according to claim 1, wherein the wavelength dependency of the transmittance of the optical filter is 5% or less. A plurality of sets of the input port, the output port, the first lens, the second lens, and the light receiving element;
A plurality of sets of the first lens and the second lens are formed on the surface of one transparent member,
The optical power monitoring apparatus according to claim 1.   9. The optical power monitoring apparatus according to claim 8, further comprising first position fixing means for fixing a relative positional relationship between each of the plurality of sets of the input port and the output port.   9. The optical power monitoring apparatus according to claim 8, further comprising second position fixing means for fixing a relative positional relationship between each of the plurality of light receiving elements. 9. The optical power monitoring apparatus according to claim 8, wherein the optical filter is provided in common for the plurality of sets of the first lens and the second lens.

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