CN101173999A - Optical fiber, optical fiber connecting method, and optical connector - Google Patents

Abstract

The present invention discloses an optical fiber, method for connecting optical fiber as well as optical connector. The optical fiber at an optical fiber connecting end has a plurality of voids around the periphery of a core, has a light-permeable substance, such as a resin or glass whose refractive index is lower than that of quartz type substances, filled in the voids adjacent the connecting end. An optical fiber connecting section where an optical fiber having a plurality of voids in a clad around the periphery of a core is connected to another optical fiber, wherein the optical fiber is connected end-to-end to aforesaid another optical fiber through a refractive index matching agent whose refractive index at the minimum temperature in actual use is lower than that of the core.

Description

The method of attachment of optical fiber, optical fiber and optical connector

The application is dividing an application of application 200480009831.X (PCT/JP2004/009619, the denomination of invention: the method for attachment of optical fiber, optical fiber and optical connector) submitted on June 30th, 2004.

The application is based on Japanese patent application No. 2003-189724,2003-189655,2003-194476,2003-189726 and 2003-346905, and the full content of these Japanese publication has been introduced in reference in this application.

Technical field

The present invention relates to around core, have the optical fiber of a plurality of emptying apertures, relate in particular to photonic crystal fiber and mould field (mode field) diameter than method of attachment and optical connector between its big single-mode fiber (single mode fiber).

In addition, the invention still further relates to and have the big core of refractive index and around the little covering of its refractive index and in this covering, have the seal construction and the encapsulating method thereof of the end on the optical fiber of a plurality of emptying apertures that extend towards the optical fiber axis direction.

In addition, the invention still further relates to have the big core of refractive index and around the little covering of its refractive index and the optical fiber that in this covering, has a plurality of emptying apertures that extend towards the optical fiber axis direction with and the joints of optical fibre.

In addition, the invention still further relates to the connecting portion of the optical fiber that the optical fiber that will have a plurality of emptying apertures in the covering around the core is connected with other optical fiber and in basket, accommodate the joints of optical fibre that this connecting portion forms.

Background technology

In the past, the general optical fiber that uses had the core that closes light inlet and covered the circumferencial direction of core and the double-layer structural of the covering that this core of refractive index ratio is slightly little, and its core, covering are all formed by quartzy based material.In this double-layer structural, because therefore the refractive index height of the refractive index ratio covering of core can be limited in core with light, and transmit in optical fiber by the gap of this refractive index.

Method of attachment by connector or mechanical splice (mechanical splice) is arranged in the method for attachment to each other of single-mode fiber.It is that each optical fiber is connected on each optical connector and the method that is easy to load and unload that connector connects, and the feature that mechanical splice connects is: will establish in thereon the V-shape groove etc. and align the end face of optical fiber, and firmly keep connected two optical fiber.The interconnection technique of common single-mode fiber is fully developed.

Recently, photonic crystal fiber (PCF:Photonic Crystal Fiber) receives much attention.

PCF has the optical fiber that photonic crystal is constructed, promptly had the periodic structure of refractive index at covering.By till this periodic structure being reduced to light wavelength or its several times degree, in crystal, import defective or local unevenness, make that light is local to be existed.

Utilize Fig. 5 that this PCF cross-sectional configuration can be described.

PCF41 is only formed by the identical covering 42 of the refractive index in optical fiber, begin from its center to arrange a plurality of cylinder emptying apertures 43 with the sub-shape of hexagonal mesh, and the length of this cylinder emptying aperture 43 spreads all over the total length of optical fiber 41.The parts that close the function of light inlet with suitable the having of core in the past are the crystal defect portions 44 as the central part of optical fiber 41.

Specifically, pure silica fibre about cladding diameter φ 125 μ m, in covering 42 from central authorities periodically with the cylinder emptying aperture 43 of the sub-shape of hexagonal mesh (4 periodic structure) configuration diameter phi 3 μ m, the heart does not form emptying aperture (crystal defect) and the core 44 that this part become close light inlet therein.

Close the strong PCF of the effect of light inlet and be used at present longly being absolutely necessary apart from the interconnection technique between the single-mode fiber (SMF:Single Mode Fiber) of high capacity communication.

The spy opens the connection end that discloses in the 2002-243972 communique by heating PCF and is installed in PCF on the lasso (ferrule) and the method for attachment between the SMF.

Yet above-mentioned method of attachment is only applicable to the PCF that the core of optical fiber is formed by the higher medium of refractive index ratio covering.In other words, the refractive index that above-mentioned method of attachment is not suitable for core and covering equates, and by photonic crystal structure (cylinder emptying aperture), ground of equal value design refractive indices is poor between core and covering, and closes the optical fiber structure of light inlet in core.This be because: when the connection end of PCF was heated, the wall of cylinder emptying aperture can be by deposited and emptying aperture is disappeared, and then cause the non-existent cause of core.In the case, the core separately of PCF and connected SMF is to be connected by the part that does not have core, therefore connects loss and increases.

On the other hand, a kind of porous optical fiber (HF:Holey Fiber) as PCF, have emptying aperture by near the cladding part the core of in the past optical fiber, reduce the actual refractive index of covering, poor by the specific refractivity that enlarges between core/covering, compare with optical fiber in the past and can significantly improve the bending loses characteristic (outside the Yao Bing " the once discussion relevant " with the practicability of porous optical fiber, letter is learned skill newspaper (society) electronic information communication association, Vol.102, NO.581, p47～50, Chang Gu river fitness " developments of photonic crystal fiber and porous optical fiber ", monthly " photon ", photon (strain) distribution, N0.7, p203～208 (2001)).

There are a plurality of emptying apertures that extend towards the optical fiber axis direction in such HF at covering, and if these emptying aperture open end, then moisture can enter wherein, the result causes the deterioration of physical strength or is caused the change of optical characteristic by the dewfall that temperature variation produces.

Open in the 2002-323625 communique the spy, for addressing these problems, disclose the method for the emptying aperture of following hermetic fiber: (1) makes covering softening, the method for flattening emptying aperture with the end face portion of deposited device (device that fiber fuse is connected by gas discharge) heating optical fiber; (2) method of insertion hardening material in hollow bulb; (3) from the outside in the method for hollow bulb mounting cover.

Yet, in the method for above-mentioned (1), seal, so the external diameter of optical fiber (cladding diameter) reduces the corresponding degree of variation with the amount of material owing to the clad material around the emptying aperture is melted the landfill emptying aperture.For example, be under the situation of 125 μ m and the emptying aperture that to have four diameters be 10 μ m when cladding diameter, if simple calculating then can draw cladding diameter and be changed to 123 μ m degree, reduce about 2 μ m.This amount is the size of the degree that departs from from the lasso internal diameter size of standard in common connector connects.In addition, be under the situation of deposited device at heating source, because therefore the temperature height of discharge gas also can be subjected to influence of evaporation at cladding surface, make physical size further reduce, and this size reduce more obvious under the bigger situation of emptying aperture total sectional area.The lasso of the cladding diameter after therefore, selection is suitable for sealing also becomes pretty troublesome.And owing to discharge gas together heats fiber end face and the cladding surface around it, so the edge of optical fiber end becomes slick and sly, the shortcoming that exists end face size on every side to change easily.

In the method for above-mentioned (2),, therefore in sclerosis portion, produce bubble owing to when the hardening material hardens, follow volumetric contraction.Space in the bubble has about 1 refractive index.So the refringence between hardening material and the bubble is apart from becoming very big, and if the big part of such variations in refractive index be near the core, then influence the waveguide road structure of optical fiber, become the reason that causes big loss.

In the method for above-mentioned (3), there is end face change in size significant disadvantages on every side.

On the other hand, in above-mentioned porous optical fiber, add man-hour carrying out connector, if directly end face is carried out attrition process, then lapping powder or lapping compound can enter in the emptying aperture of optical fiber, and also left behind after connecting processing.If carry out the connector loading and unloading repeatedly, then residual lapping powder or lapping compound might be from the emptying aperture disengagings and attached on the optical fiber lapping face.If connect to carry out connector under the state that adheres to lapping powder or lapping compound at the optical fiber lapping face, then hinder mutual the connecting airtight of connector ends, become the main cause that loss increases, and in the worst case, even abrasive surface is carried out the removal treatment of injured end face, the situation that also might can't retrieve a loss and increase.

Describe porous optical fiber (HF) once more in detail.As shown in figure 17, HF361 constitutes in the following manner, that is, in pure quartz, add germanium and the periphery of the core 362 that constitutes forms the covering 363 that is made of pure quartz, form a plurality of emptying apertures 364 (being six) that axially extend in the mode that in covering 363, surrounds core 362 in Figure 17.Though not expression in detail, HF361 is that conduct is used at the optical fibre core of the periphery formation coating of covering 363.

Core 362 is identical with the core of common single-mode fiber (SMF).Core diameters φ is that 9 μ m, cladding diameter φ are that the internal diameter φ of 125 μ m, emptying aperture 364 is 8 μ m.The refractive index of core 362 is 1.463, the refractive index of covering 363 is 1.458, the specific refractivity difference of the relative covering 363 of core 362 is identical with common SMF is 0.35% approximately.

The advantage of HF361 is: the refractive index of emptying aperture 364 is about 1, and its actual specific refractivity difference is about 32%, much larger than common SMF, therefore closes the effect height of light inlet at core 362.Therefore, HF361 has the minimum speciality of loss that for example produces with the HF361 bending time.

As shown in figure 18, the connecting portion 370 of general optical fiber via gelatinous refractive index matched agent r7, aligns the end face 361a of HF361 that removes coating and carry out the end reason and is connected with the end face 371a that removes coating and carry out the SMF371 of end reason.SMF371 is that the periphery at the core 372 with the refractive index identical with the core 362 of HF361 and same diameter has formed and has the refractive index identical with the covering 363 of HF361 and the covering 373 of same diameter.

Refractive index matched agent is in order to reduce the Fresnel reflection loss that the refringence that caused by following air layer causes and to use, and this air layer is the error when being handled by end face sometimes between the end face 371a of the end face 361a of the HF361 after aligning connection and SMF371 and the air layer that forms.

Refractive index matched agent r7 for example has the temperature characterisitic shown in the temperature characterisitic line 381 of Figure 19.In order to do one's utmost to reduce the Fresnel reflection loss, the refractive index of this refractive index matched agent r7 have near the room temperature with the refractive index of the core 372 of the core 362 of HF361 illustrated in fig. 18 or SMF371 roughly the same about 1.463.Wherein, refractive index is got different values along with the difference of wavelength, unless but specified otherwise is arranged in this manual, all adopt by n _D ²⁵The measured value of expression promptly, is used the measured value under 25 ℃ of the D line (wavelength 587.56nm) of Na.

In addition, the example as the joints of optical fibre in the past of the connecting portion 370 of up-winding fiber has holocentric mechanical splice 391 shown in Figure 20 (for example open the 2000-241660 communique with reference to the spy, the spy opens the 2002-236234 communique).Mechanical splice 391 possesses: V groove substrate 392 has the V groove that is used for relative optical fiber is aligned mutually and supports, locatees, transfers core; Cover 393 is used for overlapping at substrate 392, and the optical fiber of V groove is inserted in extruding; And the hold assembly 394 that is used for clamping substrate 392 and cover 393.

Side end at the coincidence part of substrate 392 and cover 393 is formed with wedge insertion section 395, and its two ends are formed with bullport 396.Basket 397 is made of substrate 392 and cover 393.

In mechanical splice 391, aligned position (the inner face central portion of substrate 392 and cover 393) at optical fiber is filled in Figure 18 and refractive index matched agent r7 illustrated in fig. 19 in advance, inserting wedges to wedge insertion section 395 makes form the gap between substrate 392 and cover 393, insert to this gap from bullport 396 again and carried out terminal HF361 and the SMF371 that handles, thereby in the V groove, align, afterwards, wedge is extracted, control HF361 and SMF371 with substrate 392 and cover 393, achieve a fixed connection.

Thus, can in the basket 397 of mechanical splice 391, accommodate connecting portion 370, realize that HF361 and aligning of SMF371 are connected as optical fiber illustrated in fig. 18.

Like this, because when using physical construction 391 to carry out being connected of HF361 and SMF371, the cladding diameter of HF361 and the cladding diameter of SMF371 equate, therefore can carry out with mutual being connected identically of common SMF.

Yet, in the connecting portion 370 of in the past optical fiber, be connected owing to HF361 is aligned with SMF371, so refractive index matched agent r7 can be invaded the degree of depth of hundreds of μ m by capillarity from end face 361a in each emptying aperture 364 of HF361 via refractive index matched agent r7.

The refractive index of covering 363 is 1.458, and the refractive index of each emptying aperture 364 is 1, and if to invade refractive index under the room temperature in each emptying aperture 364 be 1.463 refractive index matched agent r7, then around the core 362 of the script of central portion, form six similar cores.

Therefore, the core diameters of the reality of the HF361 after the connection, can propagates light diameter (mode field diameter: MFD) big than 9 μ m before connecting in fact.Its result, the MFD between generation and the SMF371 is poor, causes the loss that is connected of HF361 and SMF371 to become big problem.

For example, if use mechanical splice illustrated in fig. 20 391 to connect HF361 and SMF371, then wavelength is that near the connection loss room temperature of 1.55 μ m increases, is about 0.85dB.By the way, the mutual connection loss of the common SMF that core diameters is equal is about 0.1dB.

Utilize Figure 21 to represent the temperature characterisitic of connection loss of the temperature range-30～70 ℃ of the mechanical splice 391 after connection here.As shown in figure 21, at room temperature connection loss has surpassed 0.8dB after just having connected, but along with temperature rises, connects loss and return to about 0.1dB.

Recovering to connect the reason of losing at high-temperature area is, shown in the temperature characterisitic line 381 of Figure 19, refractive index matched agent r7 is along with temperature rising refractive index reduces, refractive index becomes and equates with the refractive index of covering 363 and cut down the effect of closing light inlet near 60 ℃, thereby demonstrates the cause that be connected loss equal to each other with common SMF.

On the other hand, at low-temperature region, shown in the temperature characterisitic line 381 of Figure 19, the refractive index of opposite refractive index matched agent r7 improves, therefore and the refringence between the covering 363 enlarge, increased the closing of light into effect.Thereby, by originally core 362 with invade the effect increase of closing light inlet of the substantial core that six emptying apertures 364 that refractive index matched agent r7 is arranged form, compare MFD during with room temperature and further increase, enlarged with relative SMF371 between MFD poor.Connection loss at-30～10 ℃ is very high 1dB.

Thereby mechanical splice 391 in the past has the problem that the temperature characterisitic that connects loss changes greatly, especially loses increase in the connection of low-temperature region.

Summary of the invention

Given this, first purpose of the present invention provides method of attachment and the optical connector between a kind of optical fiber, this optical fiber and the SMF of PCF type of the increase that can suppress to connect loss.

Second purpose of the present invention provides a kind of cladding diameter being maintained under the situation of just size, the waveguide road of optical fiber is not impacted and can keep the seal construction and the encapsulating method thereof of the optical fiber end of end face size on every side.

The 3rd purpose of the present invention provides a kind ofly not to be made in the emptying aperture that the lapping powder that produces when attrition process or lapping compound remain in fiber end face, can hang down loss connects and the also good optical fiber and the joints of optical fibre of long-term reliability.

The 4th purpose of the present invention provides a kind of connecting portion and joints of optical fibre that loss is little, temperature characterisitic that connect loss changes little optical fiber that connect.

On the other hand, at the connecting portion 370 or the mechanical splice 391 of optical fiber, the volume reflection of end face 361a that requires at HF361 and the end face 371a of SMF371 is little.

Thereby the 5th purpose of the present invention provides a kind of loss temperature characterisitic little with volume reflection, that be connected loss and volume reflection that connects and changes the connecting portion of little optical fiber and the connector of optical fiber.

(first scheme of the present invention)

For reaching above-mentioned first purpose, the invention provides a kind of optical fiber, comprise the core that constitutes by quartzy based material; The covering that constitutes by this quartz based material; And around the core along fiber axis to a plurality of emptying apertures, wherein be filled with the light transmission material that the low UV hardening resin of the quartzy based material of refractive index ratio is made after sclerosis near the emptying aperture connecting the end, determine the refractive index after the sclerosis, make the mode field diameter of optical fiber equal will with the mode field diameter that is connected the single-mode fiber that the end connects of optical fiber.

The preferably described emptying aperture of described optical fiber is periodically arranged with the sub-shape of hexagonal mesh from central authorities, and there is the photonic crystal fiber (PCF) of crystal defect in central authorities.

Described optical fiber can also be the porous optical fiber that has a plurality of emptying apertures that extend along the axis direction of optical fiber at core or covering.

In the described optical fiber, the refractive index after the sclerosis of UV hardening resin is 1.42.

In addition, the invention provides a kind of method of attachment of optical fiber, it is characterized in that: use V groove connector etc., on its V groove, the optical fiber that described optical fiber and mode field diameter is bigger than described optical fiber aligns and is connected.

In addition, the invention provides a kind of joints of optical fibre, it is characterized in that: described optical fiber is installed on the lasso, end face is carried out milled processed.

According to first scheme of the present invention, can obtain following effect.

(1) for the refractive index of core, covering equate, mode field diameter is much smaller than the PCF of common SMF, also can with low loss carry out with SMF between align and be connected.

(2) can prevent the strength deterioration of optical fiber or the increase of transmission loss.

(alternative plan of the present invention)

For reaching above-mentioned second purpose, the invention provides a kind of seal construction of optical fiber end, it is characterized in that: possessing the high core of refractive index and around the little covering of the refractive index of this core and there is the end of the optical fiber of a plurality of emptying apertures that extend towards the optical fiber axis direction at this covering, described emptying aperture is the both seals that the glass powder fusion below the 1 μ m constitutes by mean particle dia, and the covering external diameter of part that is formed with sealing portion is identical with the covering external diameter of the part that does not form sealing.

Described sealing can also be made of the glass with the glassy phase that constitutes optical fiber composition together.

Described sealing also can be made of the glass of the fusing point fusing point lower than the glass that constitutes optical fiber.

Described optical fiber can be fixed on the connector ring.

In addition, the invention provides a kind of encapsulating method of optical fiber end, it is characterized in that: possessing the high core of refractive index and around the little covering of the refractive index of this core and there is the end of the optical fiber of a plurality of emptying apertures that extend towards the optical fiber axis direction at this covering, form end face with the axis direction approximate vertical, from this end face to described emptying aperture insert have with the glassy phase that constitutes optical fiber with composition and mean particle dia be glass powder below the 1 μ m, after this, carry out spot heating and make described glass powder fusion the end of described optical fiber is additional, thereby seal described emptying aperture.

In addition, the invention provides a kind of encapsulating method of optical fiber end, it is characterized in that: possessing the high core of refractive index and around the little covering of the refractive index of this core and there is the end of the optical fiber of a plurality of emptying apertures that extend towards the optical fiber axis direction at this covering, form end face with the axis direction approximate vertical, insert to described emptying aperture from this end face and to have that more low melting point and mean particle dia are glass powder below the 1 μ m than the glass that constitutes optical fiber, after this, make described glass powder fusion to carrying out spot heating near the end of described emptying aperture, thereby seal described emptying aperture.

In addition, the invention provides a kind of encapsulating method of optical fiber end, it is characterized in that: possessing the high core of refractive index and around the little covering of the refractive index of this core and there is the end of the optical fiber of a plurality of emptying apertures that extend towards the optical fiber axis direction at this covering, form end face with the axis direction approximate vertical, to carrying out spot heating near the end of described emptying aperture, making mean particle dia is the following glass powder fusion of 1 μ m, thereby seals described emptying aperture.

Can to carrying out spot heating near the end of described emptying aperture, thereby seal described emptying aperture by the irradiation carbon dioxide laser.

Described optical fiber can be fixed on the connector ring in advance.

According to alternative plan of the present invention, can obtain following effect.

The seal construction of optical fiber end of the present invention is owing to be emptying aperture by the both seals that is made of glass, therefore can prevent the deterioration of the physical strength that the intrusion by moisture etc. causes and the change of the optical characteristics that caused by the dewfall that temperature variation causes.In addition, the covering external diameter of part that is formed with sealing is identical with the covering external diameter of the part that does not form sealing, therefore can be under the state of correctly keeping cladding diameter, and the waveguide road to optical fiber does not impact, and can keep end face size on every side.Therefore can easily carry out the connection between to each other connection of porous optical fiber, porous optical fiber and the common single-mode fiber.Thereby, can be corresponding with various from now on application, its result helps the development of fiber optic applications technology from now on very much.

In addition, in the encapsulating method of optical fiber end of the present invention, owing in the emptying aperture of optical fiber, insert the glass powder that has with the glassy phase that constitutes optical fiber composition together, the end of optical fiber heated make the glass powder fusion, therefore thereby the sealing emptying aperture can definitely be realized the seal construction of described optical fiber end.In addition, owing to use and the congruent glass powder of glassy phase that constitutes optical fiber, therefore the sealing that obtains is not easy to produce deformation, and reliability is superior.

And, in the encapsulating method of optical fiber end of the present invention, owing to insert the more low-melting glass powder of glass that has than constituting optical fiber to described emptying aperture, after this, make described glass powder fusion to carrying out spot heating near the end of described emptying aperture, thereby seal described emptying aperture, therefore, can select the infusible heating-up temperature of optical fiber.Therefore, can be heated to till the cladding surface, can select method commonly used in the past as heating arrangements.

In addition, in the encapsulating method of optical fiber end of the present invention, because to carrying out spot heating near the end of described emptying aperture, thereby seal described emptying aperture, therefore can just can seal the emptying aperture end without glass powder with straightforward procedure.

(third party's case of the present invention)

For reaching above-mentioned the 3rd purpose, the invention provides a kind of optical fiber, be to possess the high core of refractive index and around the little covering of the refractive index of this core and be formed with the optical fiber of a plurality of emptying apertures that extend towards the optical fiber axis direction at this core, it is characterized in that: the end at described a plurality of emptying apertures is formed with sealing, and identical with described covering or littler and diameter is that quartz below the 100nm is that the identical or littler optical adhesive of particulate and refractive index and described covering constitutes by refractive index in sealing portion.

Described quartz is that particulate can be the quartz particle with diameter of 30 to 40nm.

Described quartz is that particulate can be the quartz particle that is doped with the adjuvant that reduces refractive index.

Described optical adhesive can be the optical adhesive of UV cured property.

Can on described optical fiber, lasso be installed and constitute a kind of joints of optical fibre.

According to third party's case of the present invention, can obtain following effect.

Optical fiber of the present invention is owing to form sealing in the end of a plurality of emptying apertures, so lapping powder or lapping compound can not remain in fiber end face, thereby can provide end face the sealed joints of optical fibre that reliability is arranged.Thereby, when can provide reliability after the processing of a kind of connector to improve, the good porous optical fiber connector of optical characteristic.In addition, because sealing is that the identical or littler optical adhesive of particulate and refractive index and described covering constitutes by the refractive index quartz identical or littler with covering, therefore can prevent from the bonding agent that optical fiber end is hardened, to produce bubble, realize low lossization.

(cubic case of the present invention)

For reaching above-mentioned the 4th purpose, the invention provides a kind of connecting portion of optical fiber, it is the connecting portion that the optical fiber that will have a plurality of emptying apertures in the covering around the core is connected to the optical fiber on other the optical fiber, it is characterized in that:, described optical fiber aligned with described other optical fiber be connected via the low refractive index matched agent of the described core of refractive index ratio under the minimum temperature in actual use.

In addition, the invention provides a kind of connecting portion of optical fiber, it is the connecting portion that the optical fiber that will have a plurality of emptying apertures in the covering that is made of pure quartz around the core that is made of quartzy based material is connected to the optical fiber on other the optical fiber, it is characterized in that:, described optical fiber aligned with described other optical fiber be connected via the low refractive index matched agent of the described covering of refractive index ratio under the minimum temperature in actual use.The refractive index of the light in wavelength 1.3～1.55 μ ms band territory of described refractive index matched agent under temperature-30 ℃ is below 1.458 and the average temperature coefficient of the refractive index under temperature range-30～+ 70 ℃ is-8.0 * 10 ^-4/ ℃ more than and less than 0/ ℃.

Can in basket, accommodate the connecting portion of described optical fiber and constitute a kind of joints of optical fibre.

According to cubic case of the present invention, can provide to connect the connecting portion and the joints of optical fibre that loss is little, temperature characterisitic that connect loss changes little optical fiber.

(the 5th scheme of the present invention)

For reaching above-mentioned the 5th purpose, the invention provides a kind of connecting portion of optical fiber, it is the connecting portion that the optical fiber that will have a plurality of emptying apertures in the covering that is made of described quartzy based material around the core that is made of quartzy based material is connected to the optical fiber on other the optical fiber, it is characterized in that: via the refractive index under the temperature range in actual use is below the described covering, and containing mean diameter or average length is the refractive index match body of the following microbody of 100nm, described optical fiber is connected with described other optical fiber, and described microbody is with the particulate of pure quartz as major component.

Described refractive index match body can be to constitute by mix described microbody on described refractive index matched agent, and the mixed weight ratio between described refractive index matched agent and the described microbody is 10: 1～1: 1.

Can in basket, accommodate the connecting portion of described optical fiber and constitute a kind of joints of optical fibre.

According to the 5th scheme of the present invention, can provide a kind of loss temperature characterisitic little with volume reflection, that be connected loss and volume reflection that connects to change the connecting portion of little optical fiber and the connector of optical fiber.

Description of drawings

Fig. 1 is the side view of expression one photonic crystal fiber preferred embodiment of the present invention (PCF).

Fig. 2 (a) is the stereographic map of expression V groove connector; Fig. 2 (b) is the stereographic map that an operation of the optical fiber of V groove connector connection layout 1 and single-mode fiber is used in expression; Fig. 2 (c) is expression with the stereographic map of the state of the optical fiber of V groove connector index map 1 and single-mode fiber.

Fig. 3 is the sectional view that expression is equipped with the lasso that the FC connector of optical fiber of Fig. 1 uses.

Fig. 4 is the sectional view as the porous optical fiber of other suitable example.

Fig. 5 is a sectional view of representing photonic crystal fiber in the past.

Fig. 6 is the structure example of porous optical fiber 101 that expression is used for the seal construction of optical fiber end of the present invention, (a) is longitudinal section, (b) is cross-sectional view.

Fig. 7 is the longitudinal section of seal construction of the optical fiber end of expression embodiments of the present invention two.

Fig. 8 is the longitudinal section of seal construction of the optical fiber end of expression embodiments of the present invention three.

Fig. 9 is illustrated in the longitudinal section that optical fiber end of the present invention is installed the example of lasso.

Figure 10 is the cross-sectional view that expression is applicable to the porous optical fiber of embodiments of the present invention four.

Figure 11 is the longitudinal section of the joints of optical fibre of expression embodiments of the present invention four.

Figure 12 is the side view of connecting portion of the optical fiber of expression embodiments of the present invention five.

Figure 13 is the figure of temperature characterisitic of the refractive index of the refractive index matched agent r of expression among Figure 12.

Figure 14 is the stereographic map of the joints of optical fibre of expression embodiments of the present invention six.

Figure 15 is the figure of temperature characterisitic of the connection loss of the joints of optical fibre of expression among Figure 14.

Figure 16 is the cross-sectional view of an example of expression optical crystal optical fiber.

Figure 17 is the cross-sectional view of an example of expression porous optical fiber.

Figure 18 represents the side view of the connecting portion of optical fiber in the past.

Figure 19 is the figure of temperature characterisitic of the refractive index of expression refractive index matched agent r7 shown in Figure 180.

Figure 20 represents the stereographic map of an example of the joints of optical fibre in the past.

Figure 21 is the figure of temperature characterisitic of the connection loss of the expression joints of optical fibre shown in Figure 20.

Figure 22 is the side view of connecting portion of the optical fiber of expression embodiments of the present invention seven.

Figure 23 is the figure of the temperature characterisitic A of the refractive index of refractive index match body R among expression Figure 22.

Figure 24 is the figure of the temperature characterisitic of the expression volume reflection relevant with the joints of optical fibre of the connecting portion of the optical fiber with embodiment seven.

Figure 25 is the figure that is illustrated in the temperature characterisitic of volume reflections under the situation of using the low-refraction matching agent with characteristic shown in Figure 13, the joints of optical fibre.

Embodiment

Below, with reference to accompanying drawing, describe of the present invention preferred embodiment one in detail.

Fig. 1 is the side view of the photonic crystal fiber (PCF) of expression preferred implementation one of the present invention.

At first, the PCF11 of present embodiment is identical with PCF41 illustrated in fig. 5, therefore omit its detailed description, but, the state of the optical fibre core that the coating that optical fiber is made of the UV resin with quilt around the covering covers uses, and use in the mode of peeling its coating off the coupling part that is connected with lasso or other connectors.

As shown in Figure 1, near the link of PCF11, in 12 the emptying aperture 13, be filled with the quartzy low UV hardening resin 14 of refractive index ratio as filling material.Before UV hardening resin 14 uses is liquid at normal temperatures, hardens by irradiation ultraviolet radiation.The UV hardening resin of Shi Yonging is the fluorine-containing UV hardening resin 14 that refractive index after the sclerosis is adjusted into 1.42 epoxy system in the present embodiment.

The refractive index that is filled into the UV hardening resin 14 among the present embodiment PCF11 is 1.42, and the refractive index that forms the quartz glass of PCF11 is 1.458.The best refractive index that is filled into the material in the emptying aperture 13 is must specific refractivity 1.458 little, but that the emptying aperture diameter, emptying aperture number, emptying aperture that change PCF11 as different condition all are necessary when (density) at every turn at interval again is selected.Even the refractive index of filling material is lower but than under the big or little situation of best refractive index than the refractive index of quartz glass, increases for following reason respectively and connect loss.

When the refractive index of filling material during greater than optimum value, the specific refractivity difference of emptying aperture 13 that is filled and core (quartz) diminishes, therefore the closing into effect of light to central core dies down, and it is big that near 12 mode field diameter link (MFD:Mode Field Diameter) becomes.Thereby the MFD that produces PCF11 and SMF is bad, causes connecting loss and increases.

On the other hand, when the refractive index of filling material during less than optimum value, it is big that the emptying aperture 13 that is filled and the specific refractivity difference of core become, and therefore to the closing into the effect grow of the light of central core, 12 MFD diminishes near link.Thereby, little in the MFD change of comparing PCF11 with the MFD of the SMF of junction, produce the bad of MFD equally, cause connecting loss and increase.

Thereby, in cylinder emptying aperture 13, fill after the UV hardening resin 14, be necessary with the selected refractive index of filling material of the equal mode of each mode field diameter of PCF11 and SMF.

The production process of PCF11 then, is described.

At first peel the 15 number mm of lining portion of PCF11 off, utilize the optical fiber cutting knife that terminal part 16 is cut into vertical section, UV hardening resin 14 is coated in end face 16.The UV hardening resin 14 that is coated in end face 16 soaks into cylinder emptying aperture 13 through the capillarity of several seconds to several minutes.When soaking into, keep the time of this PCF11 to be decided by the viscosity of bonding agent 14, surperficial Zhang Li and emptying aperture diameter to a great extent.Under by the situation that grind to wait the end face 16 of pruning, be necessary to consider this amount and the length of soaking into of guaranteeing bonding agent 14, when with the section of PCF11 directly as the situation that connects end face 16 under, 100 μ m are above just very abundant.

Then, wipe away attached to the residue bonding agent 14 on the end face 16, utilize irradiation UV light such as ultraviolet lamp from the PCF11 side, make UV hardening resins 14 sclerosis that are soaked in the emptying aperture 13, finish operation with gauze etc.

Below, the method for using V groove connector to connect PCF11 and single-mode fiber (SMF:Single ModeFiber) 21 is described.

Shown in Fig. 2 (a), V groove connector is to be aligned V-shape groove 22, keep the lining maintaining part 23 of each optical fiber 11,21 at two ends and will be aligned extruding lid 24 joints of optical fibre that constitute that two optical fiber of end face push from above by what the end face to two optical fiber 11,21 aligned.

At first, shown in Fig. 2 (b), peeling quartz off is the lining portion 25 of SMF21, cuts off end face 26 with the optical fiber cutting knife.In V-shape groove 22, align the end face 26 of its SMF21 and the end face 16 of PCF11.At this moment, PCF11 and SMF21 are fixing by lining maintaining part 23 respectively.

At last, shown in Fig. 2 (c), align V-shape groove 22 and depress extruding from above and cover 24, fix two optical fiber 11,21, finish connection.

Below, the effect of present embodiment is narrated.

PCF11 is, near the link of PCF11 12, in a plurality of small emptying apertures 13, fill the low UV hardening resin 14 of refractive index ratio covering, make its sclerosis by it being carried out the ultraviolet ray irradiation, realize the purpose of sealing emptying aperture 13, therefore 12 also form the photonic crystal structure at core and covering near by the link of the PCF11 with identical refractive index, can close light inlet at the center of PCF11.

Thereby, can align with the MFD optical fiber bigger and be connected than PCF11.In the V of above-mentioned explanation groove connector 20, connect PCF11 and SMF21 to be connected loss be very low value 0.55dB.

In addition, the structure that near 12 emptying aperture 13 link of PCF11 is sealed can prevent the intrusion of when PCF end face 16 is ground lapping powder or moisture and other impurity.

As other embodiment, describe with the situation that lasso is connected with the FC connector for PCF11 with embodiment one.

The sectional view of the lasso 30 that the FC connector when Fig. 3 is expression connection PCF11 is used.

As shown in Figure 3, lasso 30 is the key element parts that constitute optical connector, and fixed part 31 that it is fixed by the PCF11 that will peel lining portion 15 off and the optical fiber maintaining part 32 that the lining portion 15 of PCF11 is installed constitute.Under the situation of using the holocentric optical connector, the FC connector is cylindrical with lasso 30.On maintaining part 31, and the lasso 30 that PCF11 is installed is connected on the optical connector PCF11 by lasso 30 and adhesive, and when being under the situation of FC connector, by fastening parts such as bolt or extrusion spring 33, is fixed on the optical connector.

The PCF11 that is filled with UV hardening resin 14 is, 12 are fixed on the fixed part 31 of sleeve pipe 30 near its link, and optical fibre core 15 is bonding in maintaining part 32, and after this, the end face 16 of adhesive portion is ground.The lasso that is connected with optical connector 30 since near the link of PCF11 12 emptying aperture 13 filled by UV hardening resin 14, therefore when grinding, can not invade lapping powder or moisture and other impurity, and the increase of the transmission that can suppress to accompany thus loss, and the tired deterioration that can suppress fiber strength is than the situation generation that accelerates usually.

Near the filling material that is filled into the link of PCF11 in 12 the emptying aperture 13 is not limited to UV hardening resin 14, can also be light transmission materials such as glass.

PCF11 is not limited only at the V groove connector 20 of above-mentioned mechanical splice etc. or FC connector can also be applicable to capillary type connector or other commercially available connector types with being suitable for of lasso 30.

In addition, the solution of the present invention not only can be used in the present embodiment the core that uses and the identical PCF11 of refractive index of covering, can also be used on the refractive index of core and the covering different PCF or porous optical fiber as shown in Figure 4 34.Porous optical fiber 34 is meant the optical fiber that has a plurality of emptying apertures 36 around core 35.Because therefore strong to patience crooked or that reverse, as to have suppressed the crooked transmission loss that causes increase can be applicable to well that diameter is little and form the optical fiber coiled cord that curls.

Below, joined accompanying drawing, to of the present invention second and the seal construction and the encapsulating method thereof of the optical fiber end of the 3rd embodiment describe.

Represented to be used in the structure example of the representational porous optical fiber 101 in the seal construction of above-mentioned optical fiber end in Fig. 6 (a) and (b).In these Fig. 6 (a) and (b), porous optical fiber 101 possesses the high core of refractive index 102 and centers on its core 102 and the little covering 103 of refractive index of formation, is formed with four emptying apertures 104 that extend towards the optical fiber axis direction near the core 102 in this covering.

Fig. 7 is the sectional view of seal construction of the optical fiber end of expression embodiment of the present invention two.In the figure, more amplify the end that has shown optical fiber than Fig. 6.In the seal construction of this optical fiber end, sealed 105 sealing of fore-end of the emptying aperture 104 that extends along axis direction.Sealing portion 105 is formed on the position that the end face of porous optical fiber 101 caves in a little, promptly is formed on from the inside a little interior location of end face.In addition, be formed with the position of sealing 105 or do not form the position of sealing 105, the external diameter of covering 103 is all just the same.Wherein, 104 sealed 105 sealings of two emptying apertures are arranged, but the end of other not shown two emptying apertures 104 is sealed too in Fig. 7.

Then, the encapsulating method to the seal construction of realizing this optical fiber end describes.

At first, after the end face of formation of the end of porous optical fiber 101 and axis direction approximate vertical, insert fine glass powder to emptying aperture 104 from its end face.Glass powder is that the material of formation optical fiber is a quartz glass, and quartzy particle diameter is preferably in below the 1 μ m.Can be by inserting fiber end face to the place of glass powder being piled into the mountain peak shape, thus glass dust is squeezed in the emptying aperture 104.In addition,, make it become pasty state, then can be inserted into more simply in the emptying aperture 104 if in glass powder, sneak into ethanol.

Then, by the irradiation carbon dioxide laser, the end of porous optical fiber 101 is heated.Because the wavelength of carbon dioxide laser is about 10 μ m, therefore can be absorbed by glass well and generate heat.As the collector lens that laser is carried out optically focused, can use in this wavelength domain transparent with zinc selenide or germanium lens as material.About the LASER HEATING optical system of such optical fiber end, the spy opens flat 7-318756 communique and is documented.By the optical system of utilizing such carbon dioxide laser, to heating simultaneously with laser near core 102 and the emptying aperture on every side 104, but focal point that also can mobile laser, and partly heat successively.Glass powder is carried out abundant fusion and stops heating, and then glass is fixed, and as shown in Figure 7, and the part that has depression at the end face of porous optical fiber 101 is formed with sealing 105.

In the sealing method, owing to the glass powder fusion is sealed emptying aperture 104, so the influx of covering material is few, can prevent that cladding diameter from changing.In addition, owing to use carbon dioxide laser as heating arrangements, therefore the enough lens light gatherings of energy system optically focused is extremely than the abundant little point of covering external diameter (generally being 125 μ m), advance the part of fire end face with the state on every side that does not heat covering, so can prevent the variation of cladding diameter by this point.In addition,, therefore be difficult in sealing 105 and produce deformation, help reliability owing to use the quartz glass that constitutes optical fiber as glass powder.

In addition, as the other method that forms sealing 105, can use the glass powder of fusing point other compositions lower than quartz glass, clamp-on in the emptying aperture 104 from the end face of porous optical fiber 101, use fully melten glass powder of heating arrangements (gas discharge of the deposited device of optical fiber, gas burner, heating wire), form sealing 105.

In this wind is sent out, also seal emptying aperture 104, so the influx of covering material is few by the melten glass powder, can prevent that cladding diameter from changing.In addition, owing to use the glass of the fusing point kind lower than quartz glass as sealant, so can select the heating-up temperature of the infusible scope of optical fiber, comprise cladding surface permission heating.Thereby, can freely select the heating arrangements in the past such as gas discharge, gas burner, heating wire of the deposited device of optical fiber as heating arrangements, and this is an advantage.Can certainly use the carbon dioxide laser heating.

Fig. 8 is the figure of seal construction of the optical fiber end of expression embodiment of the present invention three.In this end structure, sealed 106 sealing of fore-end of the emptying aperture 104 that extends along axis direction.In addition, be formed with the position of sealing 106 or do not form the position of sealing 106, the external diameter of covering 103 is all just the same.Wherein, the depression of the end of porous optical fiber 101 is compared dark a little with the depression of Fig. 7.

The method that forms sealing portion 106 is as follows, that is, after the end face of formation of the end of porous optical fiber 101 and axis direction approximate right angle, do not insert glass powder, and directly adopt the heating of utilizing above-mentioned carbon dioxide laser, and end face is carried out spot heating.Thus, by flowing into the covering material that is melted from end face, the sealing emptying aperture.

At this moment, as shown in Figure 6, because the sectional area of the open area ratio covering 103 of emptying aperture 104 is fully little, and by near the carbon dioxide laser spot heating end, therefore from the end face of porous optical fiber 101, the covering material flows into to emptying aperture 104 depths, and the end and the cladding diameter of sealing porous optical fiber 101 do not change.

Shown in Fig. 7 or 8, if the end of shaping porous optical fiber 101 then can utilize the connection method of general optical fiber, for example can utilize the mechanical connection method that becomes the application of mechanical splice V groove.In addition, can also be installed in the lasso of MT connector or holocentric connector, implement optical connector and connect.

In lasso is installed, at the lasso front end limiter is set, insert from the rear under the situation of porous optical fiber 101, as shown in Figure 9, the alignment of the end face of the end face of porous optical fiber 101 and connector ring 106.If necessary, can be in that after this situation with general optical fiber be identical, the end face of connector ring 106 is ground.

Wherein, porous optical fiber 101 can also be installed in heating again after the grinding on the connector ring 106, the sealing emptying aperture.At this moment, owing to changed the shape of porous optical fiber 101 ends, therefore can also grind again and adjust shape the end face of lasso 106 by heating.Because the sealing station of emptying aperture caves in a little than end face, therefore, the depression position of staying on the end face can be eliminated by grinding.

Below, with reference to accompanying drawing, the optical fiber and the joints of optical fibre of embodiment of the present invention four are described.

Figure 10 represents the edge face structure of the porous optical fiber 210 that embodiments of the present invention four are used.In the figure, the little covering 213 of refractive index that porous optical fiber 210 has the high core of refractive index 211 and forms around core 211, and near the core 211 of covering 213, be formed with central part with core 211 as axis of symmetry symmetry and become equally spaced four emptying apertures 215.

Usually can use 1.3 μ m band territory single-mode fiber as porous optical fiber 210.In addition, the internal diameter of emptying aperture 215 is preferably in below the above 10 μ m of 3 μ m, for example can be made as 7 μ m.The center of each emptying aperture 215 for example can be positioned at from the circumference of the center radius 12 μ m of core 211.Be filled with air or inert gas in emptying aperture 215, the refractive index in its emptying aperture 215 is 1.In addition, the refractive index of covering 213 is for example 1.458, is the high germanium of 6～9 moles of % degree that adds of refractive index than covering 213 in the core 211.

Figure 11 is the longitudinal section of the joints of optical fibre of expression embodiment of the present invention four.In the joints of optical fibre 220, sealed 221 sealing of fore-end of the emptying aperture 215 that extends towards the optical fiber axis direction of porous optical fiber 210 is equipped with lasso 223 in the periphery of porous optical fiber 210.Wherein, 215 sealed 221 sealings of two emptying apertures of porous optical fiber 210, and the end of two other not shown emptying aperture 215 is sealed too.

Sealing portion 221 is made of quartz particle and UV cured property optical adhesive.The refractive index that constitutes the quartz particle of sealing portion 221 and UV cured property optical adhesive all must equate or less than the refractive index of covering 213.Its reason below is described.

The good flexural property of porous optical fiber 210 comes from and have emptying aperture 215 near core 211, but if hypothesis is filled in refractive index ratio covering 13 higher optical materials in the emptying aperture 215 as sealing 221, then refractive index ratio covering 213 higher parts also produce in the part except core 211 originally, therefore are in the state that has a plurality of cores 211.If like this, then when the interval of the core 211 of porous optical fiber 210 and emptying aperture 215 near under other situation of light wavelength level, produce the coupling phenomenon of light, the original light of propagating in core 11 is transferred in the emptying aperture 215.The light that is transferred is propagated in sealing 221, but does not propagate in the spatial portion that does not form sealing 221, therefore becomes the reason of big loss.Therefore, preferably make the refractive index of sealing of the emptying aperture 215 of sealing porous optical fiber 210 not be higher than the refractive index of covering 213.In addition, the optical material of supposing to have the refractive index identical with covering 213 is filled in the emptying aperture 215 and under the situation as sealing 221, become just as with the common optical fiber identical construction that does not have emptying aperture 215, therefore damaged the feature with good flexural property of porous optical fiber 210.Therefore, the refractive index of the sealing 221 of the emptying aperture 215 of sealing porous optical fiber 210 is the lowest like the refractive index of covering 213.

The particle diameter that constitutes the quartz particle of sealing 221 be preferably in 1 μ m following, more preferably below 100nm, especially preferably in 30～40nm scope.If particle diameter is below the 100nm, then the volume ratio of the quartz particle in sealing 221 can rise, and, can improve the composite rate for the quartz particle of optical adhesive that is, the bubble generation rate in the time of therefore can suppressing the optical adhesive sclerosis.Quartzy identical (1.458) of the refractive index of quartz particle and the covering 213 that constitutes porous optical fiber 210, but add quartzy nano particle by the fluorine that uses interpolation fluorine in quartz particle, refractive index can be reduced-0.5～-0.7% degree.

On the other hand, can to use refractive index at room temperature be that 1.430 epoxy is UV cured property bonding agent (trade name " オ プ ト ダ イ Application 1100 " (a DAIKIN industry system)) to the optical adhesive of UV cured property.In general the refractive index of light refractive index material has temperature characterisitic, promptly, temperature improves along with reducing refractive index, therefore must consider Temperature Influence, even but above-mentioned optical adhesive about-30 ℃ of following refractive indexes also are 1.45, thereby can make its refractive index 1.458 less than covering.

The blending ratio of quartz particle and optical adhesive is: the ratio of quartz particle is high more, the generation rate of the bubble after the optical adhesive sclerosis is just low, if but ratio is too high, the then presclerotic flowability forfeiture that comprises the optical adhesive of quartz particle is difficult to fill to the emptying aperture 215 of porous optical fiber 210.Find according to the inventor's experiment, when the weight ratio of optical adhesive and quartz particle is between 1: 1～10: 1 the time, can satisfies simultaneously aspect practical and suppress the bubble generation and to the operation of the filling operation of emptying aperture 215.

The temperature characterisitic of the refractive index of quartz particle is compared little of ignoring with this characteristic of optical adhesive, therefore the overall refractive index of the sealing 221 of filling in emptying aperture 215 stably can be set at less than the quartzy level that constitutes covering 213.Therefore, can carry out stabilization to the optical characteristics that comprises flexural property.

Below, the method for making of the joints of optical fibre 220 is described.

At first, after the end of porous optical fiber 210 forms end face with the axis direction approximate vertical, insert the potpourri of quartz particles and UV cured property optical adhesive, irradiation ultraviolet radiation to emptying aperture 104 from the end face of porous optical fiber 210, the sclerosis optical adhesive forms sealing 221.Then, lasso 223 is installed on the porous optical fiber 210, the end face of porous optical fiber 210 is alignd with the end face of lasso 223.If necessary, identical then after this with the situation of general optical fiber, can also grind the end face of lasso 223.

Wherein, sealing 221, then is not particularly limited, but considers long-term reliability as long as can stop up emptying aperture 215 and have physical strength apart from the formation position of end surface of optical fiber connector, more than the preferably dark 100 μ m.

As mentioned above, according to the joints of optical fibre of present embodiment, can obtain following effect.

(1) because with the end of sealing 221 sealing emptying apertures 215, therefore can provide a kind of can be at the residual lapping powder of fiber end face or lapping compound, the sealed high joints of optical fibre of reliability of end face.

(2) because sealing 221 is made of UV cured property optical adhesive and quartz particle, therefore when optical adhesive hardens, can utilize quartz particle to suppress volumetric contraction.Therefore can prevent from the bonding agent of optical fiber end sclerosis, to produce bubble, realize low lossization.

(3) owing to utilize refractive index ratio covering 213 little sealings 221 to seal emptying apertures 215, therefore can carry out stabilization to the optical characteristics that comprises flexural property.

Below, with reference to accompanying drawing, the optical fiber connecting portion and the joints of optical fibre of embodiment of the present invention five are described.

Figure 12 is the side view of connecting portion of the optical fiber of expression suitable embodiment five of the present invention.

As shown in figure 12, the connecting portion 301 of the optical fiber of present embodiment, use with at the identical object of porous optical fiber (HF) 361 that illustrates as Figure 17 and Figure 18 and single-mode fiber 371, end face 361a for the HF361 that removes coating and carry out managing the end, via the lower refractive index matched agent r of the core 372 of the core 362 of the refractive index ratio HF361 under in actual use the minimum temperature-30 ℃ and SMF371, align with the end face 371a that removes coating and carry out the sMF371 of end reason and to be connected.

The application target of refractive index matched agent r is as follows: owing to form the air layer that the error when being handled by end causes between the end face 371a of the end face 361a of HF361 after aligning connection and SMF371, therefore using it is to lose in order to reduce the Fresnel reflection that the refringence that produced by this air layer causes.

Refractive index matched agent r for example is made of high molecular polymerization system, silicones system, uv-hardening resin.As refractive index matched agent r, the refractive index that can use the light in wavelength 1.3～1.55 μ m band territory under temperature-30 ℃ is below 1.458 and the average temperature coefficient of the refractive index under temperature range-30～+ 70 ℃ is-8.0 * 10 ^-4/ ℃ more than, less than 0/ ℃ refractive index matched agent.

Here, the average temperature coefficient of so-called refractive index is meant the per 1 ℃ refractive index variable quantity in certain temperature range.

In this example, used the transverse axis that has as shown in figure 13 get temperature (℃), the gelatinous silicon of the temperature characterisitic of the temperature characterisitic line 321 the when longitudinal axis is got refractive index is refractive index matched agent r.In more detail, temperature characterisitic line 321 is 1.455 in the refractive index under-30 ℃, is 1.435 in the refractive index under 20 ℃, is 1.417 in the refractive index under 70 ℃, the average temperature coefficient of the refractive index under temperature range-30～+ 70 ℃ is approximately-4.0 * 10 ^-4/ ℃.

The refractive index of the light in wavelength 1.3～1.55 μ ms band territory of use under temperature-30 ℃ is the refractive index matched agent r below 1.458, be to form false core, the expansion of the substantial MFD of the HF361 after preventing to connect in order to invade refractive index matched agent r in the emptying aperture 364 that prevents the HF361 after connection.

Numerical range is defined as that above-mentioned scope is considered following situation and is definite.In general, use the refractive index matched agent that constitutes by the high molecular polymerization system as refractive index matched agent r, but its refractive index has the tendency with the temperature rise and fall.-30 ℃ is the minimum temperature in the actual use, if the refractive index of refractive index matched agent r under-30 ℃ equates with covering 363 or below it, then can not form false core in the temperature province more than-30 ℃.Because the most universal quartz is the covering of optical fiber is pure quartz, therefore consider its refractive index 1.458, will be made as below 1.458 in the refractive index of the light of temperature-30 ℃.In addition, general is that the light wavelength of transmitting in the optical fiber is 1.3～1.55 μ m at quartz.

The average temperature coefficient of the refractive index of use under temperature range-30～+ 70 ℃ is-8.0 * 10 ^-4/ ℃ more than, be in order to be reduced in the reflection loss amount on connecting portion under the high-temperature area less than 0/ ℃ refractive index matched agent r.

Numerical range is decided to be that above-mentioned scope is considered following situation and is definite.+ 70 ℃ is the maximum temperature in the actual use, at this high-temperature area, might be occurred the deterioration of reflection characteristic by the refractive index reduction of refractive index matched agent r at connecting portion.Therefore the boundary of the reflection loss amount on reality is used has fixed on more than the 30dBm.Here, the reflection loss amount is the poor amount that determines by the refractive index of core 362 and refractive index matched agent r.According to the formula of Fresnel reflection, if the refractive index of core 362 is made as n1, the refractive index of refractive index matched agent r is made as n2, then reflection loss amount Lr can obtain by following formula.

Reflection loss amount: Lr=-10 * logR (dBm)

But, R=(n1-n2) ²/ (n1+n2) ²

According to this formula, when the refractive index with core 362 is made as 1.463,, be necessary refractive index matched agent r is made as more than 1.39 for guaranteeing the reflection loss amount more than the 30dBm.Temperature difference from-30 ℃ to+70 ℃ is 100 ℃, and the average temperature coefficient that refractive index matched agent r requires is-8.0 * 10 ^-4/ ℃ more than, less than 0/ ℃.

The following describes the effect of present embodiment.

In the connecting portion 301 of optical fiber since with HF361 via refractive index matched agent r, align with SMF371 and to be connected, therefore by capillarity, the refractive index matched agent r in each emptying aperture 364 of HF361 invade hundreds of μ m from end face 361a the degree of depth.

Here, shown in the temperature characterisitic line 321 of Figure 13, the refractive index of refractive index matched agent r reduces gradually along with temperature raises, and under the minimum temperature in actual use-30 ℃ is 1.455, is 1.417 under maximum temperature in actual use+70 ℃.

Thereby, the refractive index of refractive index matched agent r is in the temperature province more than-30 ℃, refractive index than the core 362 (being covering 363 in this example) of HF361 is low always, therefore, can around the core 362 of the script of central portion, not form false core even refractive index matched agent r invades in each emptying aperture 364 yet.

Therefore, the core diameters of the reality of the HF361 after the connection of the connecting portion 301 of optical fiber, to be mode field diameter (MFD) do not change before and after connecting, so the loss of the connection between HF361 and the SMF371 is little.

In the above-described embodiment, the example that HF361 is connected with SMF371 is illustrated, but also can connect two HF361.In addition, substitute the higher HF361 of refractive index that compares core 362 with covering 363, can use the equal mutually HF of refractive index of core and covering.In this case, also can obtain effect same as described above.

In addition, substitute HF361, use photonic crystal fiber (PCF) 351 as shown in figure 16, also can obtain action effect same as described above.PCF351 forms covering 353 around core 352, form a plurality of emptying apertures 354 that extend towards the direction of principal axis of core 352 with the mode honeycomb assortment around core 352 in this covering 353, constitutes the diffraction grating of photonic band-gap structure.

The number of HF that the connecting portion 301 of the optical fiber of present embodiment is not limited to use or the emptying aperture of PCF, the emptying aperture distribution diameter that in covering, distributes.

Below, the example to the eurymeric joints of optical fibre of the connecting portion 301 that contains optical fiber is described.

Figure 14 is the stereographic map of the joints of optical fibre of expression embodiments of the present invention six.

As shown in figure 14, the holocentric mechanical splice 331 of present embodiment is except using Figure 12 and refractive index matched agent r this point illustrated in fig. 13, has the formation identical with mechanical splice illustrated in fig. 20 391.

That is, mechanical splice 331 possesses: V groove substrate possesses the V groove that relative optical fiber is aligned and supports, locatees, transfers core mutually; The cover 333 of the optical fiber that inserts to the V groove is also pushed in coincidence on substrate 332; The hold assembly 334 that is used for clamping substrate 332 and cover 333.

Side end at the coincidence part of substrate 332 and cover 333 is formed with wedge insertion section 335, and its two ends are formed with bullport 336.Basket 337 is made of substrate 332 and cover 333.

In mechanical splice 331, aligned position (the inner face central portion of substrate 332 and cover 333) at optical fiber is filled in Figure 12 and refractive index matched agent r illustrated in fig. 13 in advance, inserting wedges to wedge insertion section 335 makes form the gap between substrate 332 and cover 333, insert to this gap from bullport 336 again and carried out terminal HF361 and the SMF371 that handles, thereby in the V groove, align, afterwards, wedge is extracted, control HF361 and SMF371 with substrate 332 and cover 333, achieve a fixed connection.

Thus, can in the basket 337 of mechanical splice 331, accommodate connecting portion 301, realize that HF361 and aligning of SMF371 are connected as optical fiber illustrated in fig. 12.

This mechanical splice 331 is different by the joints of optical fibre of bonding agent or the deposited method that forever connects with employing, can use repeatedly.Near the connection loss of mechanical splice 331 under wavelength 1.55 μ m, the room temperature is about 0.08dB.

The temperature characterisitic in the connection loss of temperature range-30 ℃～+ 70 ℃ of the mechanical splice 331 after here, Figure 15 represents to connect.In Figure 15, transverse axis express time, the left longitudinal axis represent temperature (℃), the right longitudinal axis represents to connect loss (dB), and will per stipulated time change 5 ℃ temperature with the black rectangle piece represent, connection loss that will this moment represents with the black diamonds piece.

As shown in figure 15, it is interior less than 0.1dB that the connection of the mechanical splice 331 after the connection is lost in whole temperature range, very stable.The refractive index that when using the so low refractive index matched agent r of refractive index, is noted that refractive index matched agent r when high-temperature area further reduces in the size of the reflection loss amount of connecting portion.Yet mechanical splice 331 is 37dBm in the reflection loss amount under+70 ℃, the boundary of the reflection loss amount on reality is used is to satisfy more than the 30dBm.

Like this, therefore mechanical splice 331 can connect HF361 and SMF371 with low loss owing to be pre-charged with refractive index matched agent r.Connect loss value and common SMF each other to be connected the loss value equal.

In addition, mechanical splice 331 is owing to be pre-charged with refractive index matched agent r, and the temperature characterisitic of the connection loss after therefore connecting is stable.The amplitude of fluctuation that connects the loss value is equal with the common SMF amplitude of fluctuation that is connected loss to each other.That is, the temperature characterisitic of the connection of mechanical splice 331 loss changes little, even it is also low especially to connect loss at low-temperature region.

Above-mentioned embodiment is an example of having represented that HF361 and SMF371 are connected by mechanical splice 331, but also can HF361 each other, PCF351 is connected by mechanical splice 331 each other with SMF361, PCF351.In the case, can obtain effect same as described above.

As the joints of optical fibre to eurymeric, the example to the mechanical splice 331 that uses the V grooved is illustrated above, but can use other V groove connectors, capillary type connector etc. all to the eurymeric joints of optical fibre.

In addition, except repeatedly used these joints of optical fibre, can also use and adopt epoxy is the joints of optical fibre of the permanent method of attachment of UV cured property bonding agent double as refractive index matched agent r.

Below, with reference to accompanying drawing, the connecting portion and the joints of optical fibre of the optical fiber of embodiments of the present invention seven are described.

At first, change the countermeasure of problem greatly as the temperature characterisitic of the connection on described mechanical splice 391 loss, present inventors have attempted using the low-refraction matching agent that the refractive index matched agent r7 of refractive index ratio Figure 18 and Figure 19 is low, defer to temperature characterisitic line 321 shown in Figure 13.This low-refraction matching agent is 1.455 in the refractive index under-30 ℃, be 1.435 in the refractive index under 20 ℃, be 1.417 in the refractive index under 70 ℃, the average temperature coefficient of the refractive index under temperature range-30～+ 70 ℃ is approximately-4.0 * 10 ^-4/ ℃.

In mechanical splice shown in Figure 20 391, substitute under the situation of refractive index matched agent r7 use low-refraction matching agent, as shown in figure 15, the connection loss under wavelength 1.55 μ m is to be 0.08dB under 20 ℃ environment.In addition, the mechanical splice 391 after the connection in the connection loss of temperature range-30 ℃～+ 70 ℃ also less than 0.1dB, very stable.

Yet what worry under the situation of using such low-refraction matching agent is, when at high-temperature area, and when the refractive index of low-refraction matching agent further reduces, the size of the reflection of light amount on the connecting portion of HF361 and SMF371.

Figure 25 is illustrated in the temperature characterisitic of the volume reflection of the mechanical splice 391 under the situation of using the low-refraction matching agent.When the relative covering of specific refractivity difference of core is equivalent to 0.35%, the refractive index of the core 362,363 of HF361 and SMF371 is 1.463, but as shown in figure 25, for example in the time of 70 ℃, the volume reflection that produces is-36dB, can not fully satisfy practical necessary-the requirement below the 40dB of.

For this reason, the inventor is through the result that concentrates on studies, expected reducing simultaneously connecting the connecting portion and the joints of optical fibre of loss and volume reflection both sides' optical fiber.

Following with reference to accompanying drawing, the embodiment of embodiment of the present invention seven is described.

Figure 22 is the side view of connecting portion of the optical fiber of expression embodiments of the present invention seven.

As shown in figure 22, the connecting portion 301 of the optical fiber of present embodiment, use with at the identical object of porous optical fiber (HF) 361 that illustrates as Figure 17 and Figure 18 and single-mode fiber 371, end face 361a for the HF361 that removes coating and carry out managing the end, via the refractive index under in actual use minimum temperature scope-30～+ 70 ℃ is that the covering of the covering 363 of HF361 and SMF371 is below 373, and containing mean diameter or average length is the refractive index match body R of the following microbody of 100nm, aligns with the end face 371a of the sMF371 that removes coating and carry out managing the end to be connected.

The application target of refractive index match body R is as follows: owing to form the air layer that the error when being handled by end causes between the end face 371a of the end face 361a of HF361 after aligning connection and SMF371, therefore using it is to lose in order to reduce the Fresnel reflection that the refringence that produced by this air layer causes.

Refractive index match body R is that for example mixing as the mean diameter of microbody in the refractive index matched agent of high molecular polymerization system or silicones system or uv-hardening resin is that shoestring, body, the corpus fibrosum of the flat that approaches 100 μ m below constitutes in the particulate below the 100nm (nanometer powder) or average length.In the present embodiment, used as refractive index match body R and in the refractive index matched agent of high molecular polymerization system, mixed the material that constitutes as the nanometer powder of major component with pure quartz.

In addition, the mixed weight ratio of refractive index matched agent and microbody is as getting 10: 1～1: 1.

Below the refractive index of the refractive index match body R of temperature range-30～+ 70 ℃ is made as the refractive index of covering 373 of the covering 363 of HF361 and SMF371 be for: even refractive index match body R invades in the emptying aperture 364 from the end face 361a of HF361, also can prevent near end face 361a to form false core, prevent from from core originally, promptly to produce the coupling phenomenon of light from the core 372 of the core 362 of HF361 and SMF371.

In general, as the refractive index matched agent of refractive index matched agent use high molecular polymerization system, but its refractive index has the tendency that rises and descend with temperature.-30 ℃ is the minimum temperature in the actual use, if therefore refractive index matched agent is below the refractive index of covering 363,373 in the refractive index under-30 ℃, even then, can near end face 361a, not form false core in the maximum temperature-70 of-30 ℃ of temperature provinces on reality is used ℃ yet.

Use that to contain mean diameter or average length be in order to prevent the at random of light as the refractive index match body R of the microbody below the 100nm.In addition, if the mean diameter of microbody or average length surpass 100nm, then when aligning HF361 and SMF371, the optical axis deviation between HF361 and SMF371 causes by axle and departs from the connection loss that causes.

As microbody use with pure quartz as the nanometer powder of major component be because: pure quartz has covering 373 refractive index about equally with covering 363 and the SM371 of HF361, almost do not have to change basicly stable cause at-30～+ 70 ℃ with the temperature characterisitic of pure quartz as the refractive index of the nanometer powder of major component.Thereby, containing with the nanometer powder of pure quartz by refractive index matched agent as major component as the high molecular polymerization system of mother metal, the temperature characterisitic that can relax the refractive index of refractive index match body R changes.

In addition, the mixed weight ratio of refractive index matched agent and microbody was made as 10: 1～1: 1st, because: when mixed weight compares less than 10: 1, by containing the DeGrain that temperature characterisitic that microbody relaxes the refractive index of refractive index match body R changes, nonsensical in practical application.In addition, if mixed weight is than surpassing 1: 1, then the viscosity of refractive index match body R improves, and is difficult to apply and install to the connecting portion of HF361 and SMF371.

Then, refractive index matching body R one example describes.

Be in the refractive index matched agent of 1.458 high molecular polymerization system, for the refractive index under-30 ℃ with the nanometer powder (SiO of ホ ソ カ ワ ミ Network ロ Application society system, particle diameter 37nm ₂Particulate) likens with the mixed weight of the refractive index matched agent of high molecular polymerization system and nanometer powder and mix, make refractive index match body R to 10: 5 mode.

As shown in figure 23, the refractive index matched agent of high molecular polymerization system have with transverse axis be made as temperature (℃), the temperature characterisitic shown in the temperature characterisitic line B that represents by dotted line of the deferring to when longitudinal axis is made as refractive index.Among the temperature characterisitic line B, be 1.458, be 1.42 in the refractive index under+70 ℃ in the refractive index under-30 ℃, the average temperature coefficient of the refractive index under temperature range-30～+ 70 ℃ is about one 4.0 * 10 ^-4/ ℃.Here, the average temperature coefficient of so-called refractive index is meant the per 1 ℃ refractive index variable quantity in certain temperature range.

In addition, refractive index match body R has the temperature characterisitic of deferring to the temperature characterisitic line A that is represented by solid line.Among the temperature characterisitic line A, be 1.458, be 1.44 in the refractive index under+70 ℃ in the refractive index under-30 ℃, the average temperature coefficient of the refractive index under temperature range-30～+ 70 ℃ is about one 2.0 * 10 ^-4/ ℃.Because refractive index match body R contains nanometer powder, the temperature characterisitic that has therefore relaxed refractive index changes, and compares with the refractive index matched agent of the high molecular polymerization system that does not contain nanometer powder, and the average temperature coefficient of refractive index becomes the value of half.

Below, the effect of present embodiment is described.

In the connecting portion 301 of optical fiber since with HF361 via refractive index match body R, align with SMF371 and to be connected, therefore by capillarity, the refractive index match body R in each emptying aperture 364 of HF361 invade hundreds of μ m from end face 361a the degree of depth.

Here, shown in the temperature characterisitic line A of Figure 23, the refractive index of refractive index match body R reduces gradually along with temperature raises, and under the minimum temperature in actual use-30 ℃ is 1.458, is 1.44 under maximum temperature in actual use+70 ℃.

Thereby, the refractive index of refractive index match body R is in the temperature province more than-30 ℃, be in below the refractive index of covering 363 of HF361 always,, also can around the core 362 of the script of central portion, do not form false core even therefore refractive index match body R invades in each emptying aperture 364.

Therefore, the connecting portion 301 of optical fiber is in the temperature range in actual use (30～+ 70 ℃), can prevent from the coupling phenomenon of the light of core (core 362 of HF361 and the core 372 of SMF371) originally.In other words, because the core diameters (mode field diameter (MFD)) of the reality of the HF361 after connecting is constant before and after connecting, so the loss of the connection between HF361 and the SMF371 is little.

In addition, connecting portion 301 at optical fiber, because containing with the temperature characterisitic of refractive index, refractive index match body R changes the pure quartz that almost do not have nanometer powder as major component, so temperature range on reality is used, the temperature characterisitic that relaxes the refractive index of refractive index match body R changes, suppressed the light reflection of the end face 371a of the end face 361a of HF361 and SMF371, thereby volume reflection is little.Therefore, can connect HF361 and SMF371 with low reflection.

In the above-described embodiment, the example that HF361 is connected with SMF371 is illustrated, but also can connect HF361 to each other.In addition, substitute the higher HF361 of refractive index that compares core 362 with covering 363, also can use the equal mutually HF of refractive index of core and covering.In this case, also can obtain effect same as described above.

In addition, substitute HF361, use photonic crystal fiber (PCF) 351 as shown in figure 16, also can obtain action effect same as described above.PCF351 forms covering 353 around core 352, form a plurality of emptying apertures 354 that extend towards the direction of principal axis of core 352 with the mode honeycomb assortment around core 352 in this covering 353, constitutes the diffraction grating of photonic band-gap structure.

The number of HF that the connecting portion 301 of the optical fiber of present embodiment is not limited to use or the emptying aperture of PCF, the emptying aperture distribution diameter that in covering, distributes.

Below, the example to the eurymeric joints of optical fibre of the connecting portion 301 that contains optical fiber is described.

As shown in figure 14, the holocentric mechanical splice 331 of present embodiment is except using Figure 22 and refractive index match body R this point illustrated in fig. 23, has the formation identical with mechanical splice illustrated in fig. 20 391.

That is, mechanical splice 331 possesses: V groove substrate possesses the V groove that relative optical fiber is aligned and supports, locatees the accent core mutually; Overlap with substrate 332, and extruding is to the cover 333 of the optical fiber of V groove insertion; The hold assembly 334 that is used for clamping substrate 332 and cover 333.

Side end at the coincidence part of substrate 332 and cover 333 is formed with wedge insertion section 335, and its two ends are formed with bullport 336.Basket 337 is made of substrate 332 and cover 333.

In mechanical splice 331, aligned position (the inner face central portion of substrate 332 and cover 333) at optical fiber is filled in Figure 22 and refractive index match body R illustrated in fig. 23 in advance, make substrate 332 and cover 333 be held the state of parts 334 clampings, inserting wedges to wedge insertion section 335 makes form the gap between substrate 332 and cover 333, insert to this gap from bullport 336 again and carried out terminal HF361 and the SMF371 that handles, thereby in the V groove, align, afterwards, wedge is extracted, control HF361 and SMF371 with substrate 332 and cover 333, achieve a fixed connection.

Thus, can in the basket 337 of mechanical splice 331, accommodate connecting portion 301, realize that HF361 and aligning of SMF371 are connected as optical fiber illustrated in fig. 22.

This mechanical splice 33 1 is different by the joints of optical fibre of bonding agent or the deposited method that forever connects with employing, can use repeatedly.Near the connection loss of mechanical splice 331 under wavelength 1.55 μ m, the room temperature is about 0.08dB.

The temperature characterisitic of the volume reflection on temperature range-30 ℃～+ 70 ℃ of the mechanical splice 331 after Figure 24 represents to connect.In Figure 24, transverse axis express time, the left longitudinal axis represent temperature (℃), the right longitudinal axis represents volume reflection (dB), and will change 5 ℃ temperature in per stipulated time and represent, volume reflection is at this moment represented with the black diamonds piece with the black rectangle piece.

As shown in figure 24, less than-41dB, the sufficient value in the practicality is (40dB) very stable relatively in whole temperature range for the volume reflection of the mechanical splice 331 after the connection.In addition, though not shown, connection under wavelength 1.55 μ m loss, also in all temperature ranges less than 0.1dB, very stable.

Like this, therefore mechanical splice 331 can connect HF361 and SMF371 with low loss and low reflection owing to be pre-charged with refractive index match body R.Connect loss value and common SMF each other to be connected the loss value equal.

In addition, mechanical splice 331 is owing to be pre-charged with refractive index match body R, and the connection loss after therefore connecting and the temperature characterisitic of volume reflection are stable.The amplitude of fluctuation of reflection value equates with the common SMF amplitude of fluctuation that is connected loss and volume reflection to each other.That is, the connection loss of mechanical splice 331 and the temperature characterisitic of volume reflection change little, even especially also low in low-temperature region connection loss and volume reflection.

Above-mentioned embodiment is an example of having represented that HF361 and SMF371 are connected by mechanical splice 331, but also can HF361 each other, PCF351 is connected by mechanical splice 331 each other with SMF371, PCF351.In the case, also can obtain effect same as described above.

As the joints of optical fibre to eurymeric, the example to the mechanical splice 331 that uses the V grooved is illustrated above, but can use other V groove connectors, capillary type connector etc. all to the eurymeric joints of optical fibre.

In addition, except repeatedly used these joints of optical fibre, can also use and adopt epoxy is the joints of optical fibre of the permanent method of attachment of UV cured property bonding agent double as refractive index match body R.

The present invention is not limited to above-mentioned embodiment.Without departing from the spirit and scope of the present invention, the various distortion in the scope that those of ordinary skills associate easily are included in the middle of the present invention.

Claims (5)

1. optical fiber possesses the high core of refractive index and is formed with along the axially extended a plurality of emptying apertures of optical fiber around the little covering of the refractive index of this core and at this covering, it is characterized in that:

End at described a plurality of emptying apertures is formed with sealing, and identical with described covering or littler and diameter is that quartz below the 100nm is that the identical or littler optical adhesive of particulate and refractive index and described covering constitutes by refractive index in sealing portion.

2. optical fiber as claimed in claim 1 is characterized in that:

Described quartz is that particulate is the quartz particle with diameter of 30 to 40nm.

3. optical fiber as claimed in claim 2 is characterized in that:

Described quartz is that particulate is the quartz particle that is doped with the adjuvant that is used to reduce refractive index.

4. optical fiber as claimed in claim 1 is characterized in that:

Described optical adhesive is the optical adhesive of UV cured property.

5. joints of optical fibre is characterized in that:

On the described optical fiber of claim 1, lasso is installed.

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