JP4276990B2 - Optical fiber collimator and optical fiber component using the same - Google Patents

Description

  The present invention relates to an optical fiber collimator and an optical fiber component using the same, and more particularly to an optical fiber collimator used for a light coupling portion in an optical device component used in optical fiber communication and an optical fiber component using the same. About.

  Recently, as optical fiber systems shift to FTTH (Fiber To The Home), the demand for bulk optical devices including optical isolators, optical switches, and other optical elements is increasing.

  In the bulk type optical device having such a configuration, the light emitted from the optical fiber is collimated by the lens and is incident on the bulk type optical device, and the light emitted from the bulk type optical device is condensed again by the lens and is optical fiber. Must be incident on the

  However, in such light coupling, a single mode fiber (hereinafter referred to as “SM fiber”) having a small core diameter is used as an optical fiber, for example, as shown in FIG. When the first SM fiber 10a, the first lens 20a, the bulk type optical device 30, the second lens 20b, and the second SM fiber 10b are arranged in combination, the light emitted from the first SM fiber 10a is the first SM fiber 10a. The first and second SM fibers 10a and 10b, the first and second lenses 20a and 20b, and the bulk type optical device 30 can be collimated with a large spot diameter by passing through one lens 20a. This complicates the alignment of the product, which takes time and increases costs. .

  For this reason, (a) as shown in FIG. 16, first and second green lenses (Gradient Index Lenses) 40 a and 40 b are arranged at both ends of the bulk type optical device 30, and the first and second green lenses are arranged. A so-called green lens system in which one end face of each of the first and second SM fibers 10a and 10b is optically connected to the end faces of 40a and 40b, respectively. (B) Both ends of the bulk type optical device 30 as shown in FIG. The first and second TECs are optically connected to one end faces of first and second fibers (hereinafter abbreviated as “TEC fibers”) 50a and 50b that have been subjected to TEC (Thermal Expanded) processing. A so-called TEC method in which one end face of each of the first and second SM fibers 10a and 10b is optically connected to the other end face of the fibers 50a and 50b, respectively. (C) As shown in FIG. 18, first and second graded index fibers (hereinafter abbreviated as “GI fibers”) 60 a and 60 b are disposed at both ends of the bulk type optical device 30. Then, a so-called GIF method has been devised in which one end face of each of the first and second SM fibers 10a and 10b is optically connected to the end faces of the first and second GI fibers 60a and 60b (for example, Patent Document 1 and Patent Document 2).

  However, in the green lens system of (A), similar to the lens system described above, although the emitted light from the SM fiber can collimate a long distance with a large spot diameter by passing through the GRIN lens, there are steps required for alignment. There was a problem that the cost increased as a whole. Further, in the (b) TEC method, the outgoing light from the SM fiber passes through the TEC fiber, so that the diffraction is small with a relatively large mode field diameter (hereinafter referred to as “MFD”). Although a corner was obtained, there was a problem that the working distance was shorter than other methods. Furthermore, in the (iii) GIF system, first, by using a GI fiber as a lens, an alignment-free and low-loss collimator can be manufactured at a low cost. Second, the length of the GI fiber is 1 / When the pitch is 4 pitches, the MFD becomes maximum, and the working distance between the collimators can be increased correspondingly. However, when the MFD exceeds a certain value, the collimating characteristics deteriorate, and the GI collimator is opposed. There was a problem that the loss worsened.

JP-A-4-21803 JP-A-6-258554

  The present invention has been made to solve the above-mentioned problems, and provides a low-loss, low-cost and easy-to-assemble optical fiber collimator from the refractive index profile of a GI fiber collimator, and an optical fiber component using the same. The purpose is to do.

An optical fiber collimator according to a first aspect of the present invention includes a TEC fiber or a coreless fiber optically connected to a tip of an SM fiber, and a GI fiber optically connected to the TEC fiber or the coreless fiber. The core diameter of the fiber is at least three times the maximum MFD of the end face of the GI fiber.

  According to a second aspect of the present invention, in the optical fiber collimator according to the first aspect of the present invention, the relative refractive index of the GI fiber is 0.6% or more.

  According to a third aspect of the present invention, in the optical fiber collimator according to the first aspect or the second aspect of the present invention, the refractive index distribution constant of the GI fiber is 1.5 to 2.5. is there.

An optical fiber component according to a fourth aspect of the present invention has an optical element having a light incident end face on one side and a light emitting end face on the other side, and one end face is optically connected to both end faces of the optical element. The first and second GI fibers, and the first and second TEC fibers or coreless fibers each having one end face optically connected to the other end face of each of the first and second GI fibers; The first and second GI fibers have first and second SM fibers each having one end face optically connected to the other end face of the second TEC fiber or coreless fiber, and the core diameters of the first and second GI fibers are: The maximum MFD of the first and second GI fiber end faces is three times or more.

  According to a fifth aspect of the present invention, in the optical fiber component according to the fourth aspect of the present invention, the optical element is composed of an optical isolator, an optical filter, an optical switch, an optical variable attenuator, or a combination thereof. It is.

  According to a sixth aspect of the present invention, in the optical fiber component according to any one of the first to third aspects of the present invention, the outer diameter of the GI fiber is 0.6 relative to the outer diameter of the SM fiber. The outer diameter is about 3 times.

  According to a seventh aspect of the present invention, in the optical fiber component according to any one of the first to third aspects of the present invention, a connector housing is attached to the tip of the GI fiber. .

  According to the optical fiber collimator of the first to seventh aspects of the present invention and the optical fiber component using the same, the optical fiber collimator can be realized by optically connecting the GI fiber to the SM fiber. It is effective in terms of low cost, alignment free, and low loss, and the core diameter of the GI fiber is set to three times or more of the MFD, so that the working distance between the collimators can be increased.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments to which an optical fiber collimator of the present invention and an optical fiber component using the same are applied will be described below with reference to the drawings. Here, FIG. 1 is an explanatory diagram of the optical fiber collimator of the present invention, and FIG. 2 shows the condition of the relative refractive index difference Δ of the GI fiber in the optical fiber collimator of the present invention.

  In FIG. 1, an optical fiber collimator of the present invention is an optical fiber collimator GI that is optically connected to an end surface of the SM fiber with its optical axis aligned, and the refractive index continuously changes in the radial direction. Fiber 2 is provided.

  The SM fiber 1 includes a core 11 for propagating light and a clad 12 provided on the outer periphery of the core 11. Similarly, the GI fiber 2 includes a core 21 for propagating light and an outer periphery of the core 21. And a clad 22 provided.

  The SM fiber 1 and the GI fiber 2 are fusion-bonded by heating the connection end surfaces of both mirror-finished surfaces with a burner or arc discharge.

  In the optical fiber collimator having such a configuration, light incident from the input end of the SM fiber 1 propagates through the SM fiber 1 in a small MFD state H1 and is emitted from the output end of the SM fiber 1. The light emitted from the SM fiber 1 is incident on the input end of the GI fiber 2 and is expanded to a large MFD state H2 in the GI fiber 2, and propagates through the GI fiber 2 in a single mode to light from an optical element (not shown). Incident on the incident end face.

  Here, the outer diameter (hereinafter referred to as “core diameter”) D of the core 21 of the GI fiber 2 is set to be not less than three times the maximum MFD of the end face of the GI fiber 2 for the reason described later. The relative refractive index difference (Δ) is set to 0.6% or more as shown in FIG.

  By the way, when the GI fiber 2 is optically connected to the end face of the SM fiber 1, the light emitted from the SM fiber 1 has an increased light intensity in the GI fiber 2, and the spreading method is based on the refractive index of the GI fiber 2. If the distribution is a square distribution (α = 2), it can be expressed by Equation 1.

ｎ０：クラッドの屈折率、ｒ：径方向の位置、a：コア半径
また、式１は、ＧＩファイバが理想的な２乗分布と仮定すると、式２のように変換することができる。 However,

n0: Refractive index of clad, r: radial position, a: core radius Further, Equation 1 can be converted into Equation 2 assuming that the GI fiber has an ideal square distribution.

However, 2w ₁ : MFD of propagating light incident from SM fiber 1, w ₂ : 1/4 of GI fiber
MFD at pitch length, Δ: peak relative refractive index difference of GI fiber, 2a: core diameter, λ: wavelength The MFD in GI fiber 2 is shown in FIG. It changes as shown. In this case, the conditions of the GI fiber 2 are Δ = 0.85% and the core diameter D = 106 μm.

Here, the length of the GI fiber 2 that is ¼ pitch (hereinafter referred to as “¼ pitch length”).
) Has the maximum MFD at about 600 μm, but in the actual GI fiber 2, the refractive index distribution is not an ideal square distribution (α = 2), so the theoretical calculation of Equation 2 is not applicable.

  Next, the reason why low loss propagation is realized when the optical collimators having such a configuration are opposed to each other will be described.

  First, the reason why it is preferable that the core diameter D of the GI fiber 2 is three times or more of the MFD is that the portion of the propagation light distribution in the GI fiber 2 that overlaps the cladding 22 becomes larger, which is due to reflection from the cladding 22. This is because the mode becomes large and loss occurs. Therefore, if the core diameter D of the GI fiber 2 is not less than 3 times the MFD (hereinafter referred to as “D ≧ 3 × MFD”), the influence of the mode due to the reflection from the clad 22 is not required even if it is not an ideal α power distribution. It becomes hard to receive, and even if it makes it face as a collimator, a loss will not increase.

  The reason why the refractive index profile multiplier α of the GI fiber is preferably in the range of 1.5 to 2.5 is that the propagation light is satisfied when α is in the range of 1.5 to 2.5 under the condition of D ≧ 3 × MFD. This is because the loss does not increase even if it is affected by the aberration.

By the way, as described above, the inventors' experiments show that there is a difference between the theoretical MFD of the GI fiber 2 (hereinafter referred to as “theoretical MFD”) and the actually measured MFD (hereinafter referred to as “measured MFD”). It became clear from. Specifically, the theoretical MFD with Δ = 0.85% and the core diameter D of 104 μm is 58 μm, but the actually measured MFD is 32 μm. In other words, from the experiment, if the measured value is w ₂ ′, there is a relationship of w ₂ ′ = 0.55 × w ₂ , and therefore, the above equation 2 can be expressed as equation 3, When the relationship between the MFD and the core diameter D is changed, it can be expressed as shown in Equation 4.

However, w ₁ = 5.25 μm, λ = 1.55 μm, and n ₀ = 1.444.

  Considering the above points, a fiber structure that satisfies the condition D ≧ 3 × MFD can be obtained from Equation 4.

FIG. 4 shows the relationship between the core diameter D and MFD when Δ obtained from Equation 4 is changed.
Here, the horizontal axis indicates the core diameter D (μm) of the GI fiber 2, and the vertical axis indicates the MFD (μm) of the GI fiber 2. In the drawing, L1 is Δ is 0.1%, and L2 is Δ Is 0.2%, L3 is Δ is 0.3%, L4 is Δ is 0.4%, L5 is Δ is 0.5%, L6 is Δ is 0.6%, L7 is Δ is 0.7%
%, L8 indicates the design range when Δ is 0.8%, and L9 indicates each design range when Δ is 0.9%.

  From the figure, since L6 of the thick line in the figure is D = 3 × MFD, in order to produce a low-loss collimator that satisfies the condition of D ≧ 3 × MFD, an area below the thick line L6 (for example, L6 L9), that is, the GI fiber 2 with Δ ≧ 0.6% satisfies the design condition.

  Next, various examples will be described in the case where a GI fiber that satisfies the condition of Δ ≧ 0.6% or a GI fiber that does not satisfy the condition of Δ ≧ 0.6% is fused to a normal SM fiber. .

  First, as a first connection example, an example in which a normal SM fiber and a GI fiber satisfying a condition of Δ ≧ 0.6% are fusion-bonded will be described.

  FIG. 5 shows the relationship between the refractive index profile of the GI fiber having an α value of about 2 and the MFD. In the figure, the horizontal axis indicates the radius (μm) of the GI fiber, the vertical axis indicates the light intensity and the relative refractive index difference. In the figure, L10 is the relative refractive index difference Δ, and L11 is the 1/4 pitch length. The light intensity distribution in the GI fiber, L12 indicates the light intensity distribution in the GI fiber having a ½ pitch length, L13 indicates the MFD range, and L14 indicates the core diameter D range.

  When the GI fiber 2 satisfying the condition that α value is 2 and Δ ≧ 0.6% or more is fusion-spliced to the transmission SM fiber 1 with a 1/4 pitch length, as shown in FIG. The size of D became 3 times or more of MFD. Here, the MFD of the end face of the GI fiber having a 1/4 pitch length was 30 μm, the core diameter D was 106 μm, and Δ was 0.85%.

  Further, as shown in FIG. 6, the SM fiber 1 (hereinafter, the left SM fiber 1 in the figure is referred to as “first SM fiber 1a” and the right SM fiber 1 is connected to both ends of the ½ pitch length GI fiber 2, as shown in FIG. Is referred to as “second SM fiber 1b”) and its connection loss is measured. As shown in FIG. 7, the connection loss is 0.1 dB or less, which is the minimum value in the figure. A low-loss collimator was obtained, and a value with no problem even when applied to a transmission SM fiber was obtained. In FIG. 6, reference numerals H1a and H1b denote intensity distributions of light propagating in the first and second SM fibers 1a and 1b in a small MFD state, and H2 propagates in the GI fiber 2 in a large MFD state. The light intensity distribution is shown.

  Next, as a second connection example, an example in which a normal SM fiber and a GI fiber that does not satisfy the condition of Δ ≧ 0.6% are fusion-bonded will be described.

When the α value is 2.4 and the GI fiber 2 that does not satisfy the condition of Δ ≧ 0.6% or more is fusion spliced to the transmission SM fiber 1 with a 1/2 pitch length, the connection loss is shown in FIG. As shown, it deteriorates to 0.5 dB or more, so that it is difficult to apply it to a communication system as a collimator. In this case, the MFD at the end face of the GI fiber at the 1/2 pitch length is 60 μm, the core diameter D is 100 μm, Δ is 0.5%, and the core diameter D is 1.67 times the MFD. It will be well below 3 times.

  Next, as a third connection example, an example in which a TEC-processed fiber and a GI fiber satisfying a condition of Δ ≧ 0.6% are fusion-bonded will be described.

  When the GI fiber 2 satisfying the condition that α value is 2 and Δ ≧ 0.6% or more is fused with a fiber having a 1/4 pitch length and a TEC-processed end of the transmission SM fiber 1, the core diameter D became more than 3 times MFD. Also, as shown in FIG. 9, one end of the first and second TEC-treated fibers 3a and 3b is optically connected to both ends of the GI fiber 2, and the first and second TEC-treated fibers 3a. When the first and second transmission SM fibers 1a and 1b were optically connected to the other end of 3b, the connection loss had a minimum value of 0.1 dB or less, and a low-loss collimator was obtained. In FIG. 9, symbols H1a and H1b are the intensity distributions of light propagating through the first and second SM fibers 1a and 1b in a small MFD state as in FIG. 6, and H3a and H3b are subjected to TEC processing. The intensity distribution of light propagating in the fibers 3a and 3b in a state of MFD larger than H1a and H1b, H2 indicates the intensity distribution of light propagating in the state of large MFD in the GI fiber 2 as in FIG. Yes.

  Next, as a fourth connection example, an example in which a coreless fiber and a GI fiber satisfying the condition of Δ ≧ 0.6% are fusion-bonded will be described. Here, the coreless fiber is a single refractive index fiber made of pure silica glass.

  When the GI fiber 2 having an α value of 2 and satisfying the condition of Δ ≧ 0.6% or more is fused with a coreless fiber connected to the tip of the transmission SM fiber 1 with a 1/4 pitch length, the core diameter D became more than 3 times MFD. Further, as shown in FIG. 10, one end of the first and second coreless fibers 4a and 4b is optically connected to both ends of the GI fiber 2, and other than the first and second coreless fibers 4a and 4b. When the first and second transmission SM fibers 1a and 1b were optically connected to the ends, the connection loss had a minimum value of 0.1 dB or less, and a low-loss collimator was obtained. In FIG. 10, reference numerals H1a and H1b denote the intensity distribution of light propagating in a small MFD state in the first and second SM fibers 1a and 1b, similarly to FIG. 6, and H4a and H4b denote coreless fibers 4a, The intensity distribution of light propagating in the state of MFD larger than H1a and H1b in 4b, H2 shows the intensity distribution of light propagating in the state of MFD larger in the GI fiber 2 as in FIG. Here, the outer diameter of the SM fiber, the coreless fiber, and the GI fiber is 125 μm. Although the coreless fiber is used in this connection example, an air layer (space propagation layer) may be used instead of the coreless fiber.

  From the above various examples, according to the optical fiber collimator of the present invention, the core diameter D is 3 times or more of the MFD, and the connection loss is 0.1 dB or less, so that a low-loss collimator can be obtained. I understand.

  Next, an optical fiber component using the optical fiber collimator of the present invention will be described.

  FIG. 11 shows a schematic view of an optical fiber component in the first embodiment of the present invention. In the figure, parts common to those in FIGS. 1 to 10 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 11, the optical fiber component of the present invention satisfies the condition of Δ ≧ 0.6% and the optical element 5 composed of an optical isolator, an optical filter, an optical switch, an optical variable attenuator, or a combination thereof. A pair of GI fibers 2 (hereinafter, the left GI fiber 2 is referred to as "first GI fiber 2a" and the right GI fiber 2 is referred to as "second GI fiber 2b"), first and second SM fibers 1a and 1b are provided, and one end face of the first GI fiber 2a (output end) is optically connected to one end face of the optical element 5 so as to coincide with the optical axis of the optical element 5. Then, one end face (input end) of the second GI fiber 2b is optically connected to the other end face so as to coincide with the optical axis of the optical element 5. Further, the other end face (input end) of the first GI fiber 2a is optically aligned with the one end face (output end) of the first SM fiber 1a aligned with the optical axis of the first GI fiber 2a. Connected to the other end face (output end) of the second GI fiber 2b, one end face (input end) of the second SM fiber 1b is optically aligned with the optical axis of the second GI fiber 2b. It is connected to the. The first and second GI fibers 2a and 2b and the first and second SM fibers 1a and 1b are fusion-bonded by heating the connection end surfaces of both mirror-finished surfaces with a burner or arc discharge. In addition, the first and second GI fibers 2a and 2b and the optical element 5 can be optically connected by applying an optical adhesive or matching oil. The SM fiber has an outer diameter of 125 μm, and the GI fiber has an outer diameter of 250 μm. Here, the outer diameter of the GI fiber is preferably 0.6 to 3 times the outer diameter of the SM fiber. This is because if it is less than 0.6 times or more than 3 times, stable connection becomes difficult and the loss at the connection interface may increase.

  In the optical fiber component having such a configuration, the light incident on the first SM fiber 1a propagates through the first SM fiber 1a in a small MFD state and is incident on the first GI fiber 2a. The GI fiber 2a is enlarged to a large MFD state, propagates through the first GI fiber 2a in a single mode, and enters the optical element 5. The light incident on the optical element 5 is incident on the second GI fiber 2b, propagates in the second GI fiber 2b in a large MFD state, and is incident on the second SM fiber 1b. The second SM fiber 1b is reduced to a small MFD state and propagates through the second SM fiber 1b.

  According to such an optical fiber component, an optical fiber collimator can be realized simply by connecting the first and second GI fibers 2a and 2b to the first and second SM fibers 1a and 1b. This is effective in terms of alignment free and low loss, and the core diameter D of the first and second GI fibers 2a and 2b is set to be three times or more of the MFD, so that the working distance between the collimators is reduced. It can be made longer.

  FIG. 12 is an explanatory diagram of optical fiber components in the second embodiment of the present invention. In the figure, parts common to those in FIGS. 1 to 11 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, the optical fiber collimator shown in FIG. 1 is provided.

  The outer diameter of the GI fiber 2 can be appropriately selected between 80 μm and 2.5 mm, for example. Similarly, the outer diameter of the SM fiber 1 can be appropriately selected between 80 μm and 2.5 mm, for example. Here, when the outer diameter of the SM fiber or the GI fiber is either 1.25 mm or both, the outer diameter of the ferrule of the MU connector is the same as 1.25 mm. Physical Contact) is possible. It should be noted that the outer diameter of the SM fiber and the GI fiber is preferably in the range of 80 μm to 2.5 mm. However, if it is less than 80 μm, the fiber becomes too thin, causing a problem in strength, and handling becomes difficult. This is because if it exceeds 2.5 mm, the flexibility becomes poor and the handling becomes difficult.

  FIG. 13 is an explanatory view of an optical fiber component in the third embodiment of the present invention. In the figure, parts common to those in FIGS. 1 to 12 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, a pair of optical fiber components shown in FIG. 12 is provided.

  In this embodiment, the optical fiber collimator shown in FIG. 1 is inserted into the ferrules 7a and 7b through the adapter 6 so as to face each other. Bonding can be performed easily.

  FIG. 14 is an explanatory diagram of optical fiber components in the fourth embodiment of the present invention. In the figure, parts common to those in FIGS. 1 to 13 are denoted by the same reference numerals and detailed description thereof is omitted.

  In this embodiment, the optical fiber collimator shown in FIG. 1 is provided.

  A connector housing 8 is attached to the outer periphery of one end portion (tip portion) of the GI fiber 2, and the tip surface of the GI fiber 2 is disposed so as to slightly protrude from the end surface of the connector housing 8. Yes. In the figure, reference numeral 9 denotes a threaded portion.

  In this embodiment, the distal end portion of the GI fiber 2 is formed in a plug shape by attaching the connector housing 8, so that the distal end portion of the GI fiber 2 can be connected to the adapter 6.

  The present invention is not limited to the above-described embodiments, and can be modified and modified as follows, for example, within the scope of the claims of the present invention.

  First, in the above-described embodiments, the case where the outer diameter of the GI fiber is equal to the outer diameter of the SM fiber, and the case where the outer diameter of the former is different from the outer diameter of the latter are described. Considering workability and material cost, it is optimal to fuse and connect a normal SM having a fiber diameter of 125 μm and a GI fiber having a fiber diameter of 125 μm.

  Second, the GI fiber according to the present invention has an ideal refractive index distribution of squared refractive index (α = 2), but when the distribution function α is fitted over the entire core diameter, 1.5 <α <2 A range of .5 is also acceptable.

  Third, the core diameter of the GI fiber in the present invention is not particularly defined.

  Fourth, the SM fiber used on the incident side of the GI fiber in the present invention is not only equivalent to a normal single mode optical fiber (SMF28 or equivalent), but also a high NA (numerical aperture) -SM fiber, photonic. Crystal fiber, DSF (dispersion shifted optical fiber), NZ-DSF (non-zero dispersion shifted fiber), or NSP (Non-Strippable Primary Coated) fiber may be used.

  Fifth, as a material of the GI fiber in the present invention, a material that increases the refractive index by adding Ge to quartz base glass is usually used, but P (phosphorus), B (boron), La (lanthanum), Al (Aluminum) and F (fluorine) may be co-added. Further, the refractive index distribution may be adjusted using a material using a plastic resin.

  Sixth, the length of the GI fiber in the present invention varies depending on the core diameter, the peak refractive index, and the size of the MFD on the incident side, but may be about 50 μm to 5 cm due to workability.

  Seventh, the connection between the SM fiber and the GI fiber is not limited to the fusion-spliced connection, and may be, for example, a PC contact or a mechanical splice.

  Eighth, the SM fiber may have a tapered shape, or may be properly used depending on the state of optical connection with the transmission GI fiber.

  Ninth, the functional part of the optical fiber collimator may add SM fiber having a large MFD by fusion splicing, PC connection or mechanical splicing.

Explanatory drawing of the optical fiber collimator of the present invention Explanatory drawing which shows the refractive index distribution of the core of GI fiber in the optical fiber collimator of this invention. Explanatory drawing which shows the change state of MFD of the longitudinal direction in GI fiber. Explanatory drawing which shows the example of the design range of GI fiber. Explanatory drawing which shows the relationship between refractive index distribution and MFD of GI fiber whose alpha value is 2 vicinity. Explanatory drawing which shows the connection loss measurement system of SM fiber and GI fiber. Explanatory drawing which shows the connection loss measurement result of SM fiber and GI fiber. Explanatory drawing which shows the connection loss measurement result of SM fiber and GI fiber which does not satisfy predetermined conditions. Explanatory drawing which shows the connection loss system of a TEC fiber and GI fiber. Explanatory drawing which shows the connection loss system of a coreless fiber and GI fiber. Explanatory drawing which shows the optical fiber component in 1st Example of this invention. Explanatory drawing which shows the optical fiber component in the 2nd Example of this invention. Explanatory drawing which shows the optical fiber component in the 3rd Example of this invention. Explanatory drawing which shows the optical fiber component in the 4th Example of this invention. Explanatory drawing of the conventional optical fiber component. Explanatory drawing of the conventional optical fiber component. Explanatory drawing of the conventional optical fiber component. Explanatory drawing of the conventional optical fiber component.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b ... SM fiber 2, 2a, 2b ... GI fiber 5 ... Optical element 8 ... Connector housing D ... Core diameter

Claims (7)

A TEC fiber or coreless fiber optically connected to the tip of a single mode fiber, and a graded index fiber optically connected to the TEC fiber or coreless fiber ;
The core diameter of the graded index fiber is at least three times the maximum mode field diameter of the end face of the graded index fiber.   The optical fiber collimator according to claim 1, wherein a relative refractive index of the graded index fiber is 0.6% or more.   The optical fiber collimator according to claim 1 or 2, wherein a refractive index distribution constant of the graded index fiber is 1.5 to 2.5. An optical element having a light incident end face on one side and a light emitting end face on the other; first and second graded index fibers each having one end face optically connected to both end faces of the optical element; The first and second TEC fibers or coreless fibers each having one end face optically connected to the other end face of each of the first and second graded index fibers; and the first and second TEC fibers or First and second single-mode fibers each having one end face optically connected to the other end face of the coreless fiber ;
An optical fiber component wherein the core diameter of the first and second graded index fibers is at least three times the maximum mode field diameter of the end faces of the first and second graded index fibers.   5. The optical fiber component according to claim 4, wherein the optical element includes an optical isolator, an optical filter, an optical switch, an optical variable attenuator, or a combination thereof.   4. The outer diameter of the graded index fiber is 0.6 to 3 times the outer diameter of the single mode fiber. 5. Optical fiber parts.   The optical fiber component according to any one of claims 1 to 3, wherein a connector housing is attached to a tip portion of the graded index fiber.

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