JP4344663B2 - Optical connector - Google Patents

Description

  The present invention relates to an optical connector used for optical communication and the like for connecting optical fibers to each other.

  Conventionally, in datacom communications, 10 megabit Ethernet (registered trademark) and 100 megabit Fast Ethernet (registered trademark) have been widely used as systems for connecting computers, and the transition to Gigabit Ethernet (registered trademark), which has a larger transmission capacity. In addition, development of 10 Gigabit Ethernet (registered trademark) has been started for future ultrahigh-speed and large-capacity transmission.

  As the biggest feature of Gigabit Ethernet (registered trademark) and 10 Gigabit Ethernet (registered trademark), the popular Ethernet (registered trademark) system has been introduced, and the system itself is already in mass production. It is cheap compared to the system, and it is a high-speed, large-capacity gigabit.

  In other words, Gigabit Ethernet (registered trademark) and 10 Gigabit Ethernet (registered trademark) use the same frame format as 10 megabit Ethernet (registered trademark) and 100 megabit Fast Ethernet (registered trademark), and simply increase the transmission speed. (Registered trademark).

  Therefore, it is possible to perform a 10 mega, 100 mega, 1 giga, and 10 giga seamless communication network expansion.

  When the transmission capacity is increased to 10 megabits, 100 megabits, 1 gigabit and 10 gigabits in this way, the transmission method is an electrical signal followed by an optical signal of light emitting diode light emission, and then a laser diode (hereinafter LD). ) Change to light emission optical signal, and the communication cable must be changed to copper wire, multimode optical fiber, single mode optical fiber.

  However, communication cables are difficult to replace easily, especially in North America, where a network of multimode optical fibers is stretched.

  For this reason, there is a growing trend to promote Gigabit Ethernet (registered trademark) capable of high-speed and large-capacity transmission using the existing multimode optical fiber cable network and in the future 10 Gigabit Ethernet (registered trademark). .

  However, when the LD light is incident on the multimode optical fiber, the spot size of the LD light is small relative to the core diameter of the multimode optical fiber, so that the core is not filled with light and is not excited well.

  For this purpose, a method has been adopted in which LD light is directly incident on a single-mode optical fiber and this is joined to an existing multimode optical fiber.

  However, when the single mode optical fiber and the multimode optical fiber that have received the LD light are connected, some of the modes are dispersed, and various signals interfere with each other, making it impossible for the receiver to receive an accurate signal. Therefore, there is a problem that the transmission distance becomes extremely short.

  The multi-mode optical fiber is of a graded index type, and as shown in FIG. 5 (a), the core refractive index has been devised to form a radiation type for the purpose of aligning the arrival time of each mode. It is designed so that there is no dispersion due to mode differences.

  However, since an actual multimode optical fiber has a “hollow” portion having a low refractive index at the center portion as shown in FIG. 5B in the manufacturing process, some of the modes of incident light are This is because various signals interfere with each other and the above phenomenon occurs.

  For this reason, there is a problem that a long transmission distance cannot be obtained even when LD light is used as the folding light source.

  Therefore, as shown in FIG. 6, the conventional optical connector 40 will be described as an FC type optical connector as an example, which is a pair of optical fiber fixtures 33 and 33 ′ brought into contact with each other. The optical fiber fixtures 33 and 33 ′ include ferrules 31 and 31 ′ having shaft holes 31 a and 31 a ′ through which the optical fibers 41 and 41 ′ are inserted and fixed, and concave portions 32 a into which the ferrules 31 and 31 ′ are fitted. And a ferrule support 32 having a through hole 32b coaxial with the shaft holes 31a and 31a 'of the ferrules 31 and 31'. The shaft holes 31a and 31a 'of the ferrules 31 and 31' are interlocked with the recesses 32a. The optical fibers 41 and 41 ′ are inserted, and the optical fibers 41 and 41 ′ are fixed by filling the through holes 32 b of the ferrule support 32 with the adhesive 43. It was the.

  The pair of ferrules 31, 31 ′ are held by a sleeve 44, and an adapter coupling 45 having screw portions at both ends is disposed on the outer periphery of the sleeve 44, and a coupling nut 46 is attached to the screw portion of the adapter coupling 45. By screwing together, the front end surfaces of the ferrules 31 and 31 ′ of the optical fiber fixtures 33 and 33 ′ are brought into contact with each other by the pressing force of the spring 47 disposed between each coupling nut 46 and the ferrule support 32. The tip surfaces of the optical fibers 41 and 41 ′ are optically connected to each other.

  The sleeve 44 has a cylindrical shape in which the inner diameter is arranged substantially parallel to the outer diameter and is connected in a straight line from one end of the open end to the other.

  The entrance-side ferrule 31 has a shaft hole 31a at the substantially central position of the outer periphery thereof, and a single mode optical fiber 41 is bonded and fixed to the shaft hole 31a. A shaft hole 31 ′ is provided at a position eccentric from the center, and a multimode optical fiber 41 ′ is bonded and fixed to the shaft hole 31 a ′, and the tip surfaces of the ferrules 31 and 31 ′ are the inner diameter of the sleeve 44. It was fixed inside.

Therefore, the center position of the single mode optical fiber 41 and the center position of the multimode optical fiber 41 ′ are decentered, and the light passing through the single mode optical fiber 41 is as shown in FIG. 5B. The center part of 'is not incident on the concave part where the refractive index is low, so that it does not cause anomalous dispersion of the mode and signals can be transmitted efficiently without interference (Patent Document) 1).
JP 2001-13375 A

  However, the center positions of the cores of the pair of optical fibers shown in FIG. 6 are connected so as to be relatively eccentric, and in particular, the single mode optical fiber 41 is arranged on one of the pair of optical fibers, and the multimode fiber 41 is arranged on the other side. In the conventional optical connector 40 in which 'is arranged, a single mode optical fiber 41 is used if the Ethernet (registered trademark) has a transmission speed up to 10 megabit, 100 megabit Fast Ethernet (registered trademark), and 1 gigabit Ethernet (registered trademark). The light that has passed through is removed from the central portion of the multi-mode optical fiber 41 ′, such as a concave portion having a low refractive index, so that abnormal dispersion of modes does not occur, and the signal does not interfere efficiently. In recent years, there has been a demand for a transmission distance of up to 550 m, and 10 gigabit Ethernet. (Registered trademark), at a transmission distance of 550 m, some of the modes of incident light are dispersed, and various signals interfere with each other, making it impossible to receive an accurate signal at the light receiver. It has also occurred.

In view of the above problems , the present invention provides an optical connector for connecting the end faces of a pair of optical fibers, one of which is a single mode optical fiber and the other is a multimode optical fiber . The center positions are abutted so as to be decentered within a range of 10 to 25 μm , and the incident beam from one optical fiber is tilted within a range of 3 to 25 ° with respect to the axis of the other optical fiber. By making the light incident, the two are optically connected , the eccentric direction of the center position of the core is the X axis, the axial direction of the optical fiber is the Z axis, and the direction perpendicular to the X axis and the Z axis is the Y axis. When the Y-axis and the Z-axis are offset by the amount of eccentricity in which the center positions of the cores are decentered from each other, the Y'-axis and the Z'-axis are the incident beams. ' It is characterized by being in the plane formed by the axis .

In addition, the pair of optical fibers are brought into contact with each other so that the center position of the core is decentered within a range of 15 to 20 μm .

  The ferrule holding at least one of the end portions of the optical fiber eccentric from the center position of the ferrule is inserted into a cylindrical sleeve having an inner hole bent at a substantially central portion. To do.

Thus, according to the present invention, in the optical connector for connecting the end faces of a pair of optical fibers , one of which is a single mode optical fiber and the other is a multimode optical fiber, the center of the core of the pair of optical fibers is used. The position is relatively decentered within a range of 10 to 25 μm, and an incident beam from one optical fiber is inclined and incident within a range of 3 to 25 ° with respect to the axis of the other optical fiber, When the two are optically connected, the eccentric direction of the center position of the core is the X axis, the axial direction of the optical fiber is the Z axis, and the direction perpendicular to the X axis and the Z axis is the Y axis. The incident beam is a plane formed by the Y ′ axis and the Z ′ axis, when the Y ′ axis and the Z ′ axis are the axes shifted from each other by the amount of eccentricity in which the center positions of the core and the Z axis are offset from each other. by is an internal, single-mode optical file The light that has passed through the optical path enters the central portion of the multimode optical fiber after removing the low refractive index indentation, so that the abnormal dispersion of the mode does not occur and the signal does not interfere efficiently. Can be transmitted.

  Embodiments of the present invention will be described below with reference to the drawings.

  Fig.1 (a) is sectional drawing of the optical connector which shows 1st embodiment of this invention.

  The optical connector 10 according to the present invention will be described as an FC-type optical connector, which is a pair of optical fiber fixtures 3 and 3 'that are brought into contact with each other. The optical fiber fixtures 3 and 3 ′ include ferrules 1 and 1 ′ having shaft holes 1a and 1a ′ through which the optical fibers 11 and 11 ′ are inserted and fixed, and a recess 2a in which the ferrules 1 and 1 ′ are fitted. And a ferrule support 2 having a through hole 2b coaxial with the shaft holes 1a and 1a 'of the ferrules 1 and 1'. The optical fibers 11, 11 ′ are inserted and the through holes 2 b of the ferrule support 2 are filled with the adhesive 3 to fix the optical fibers 1, 1 ′.

  The pair of ferrules 1, 1 ′ are held by a sleeve 14, and an adapter coupling 15 provided with screw portions at both ends is disposed on the outer periphery of the sleeve 14, and a coupling nut 16 is attached to the screw portion of the adapter coupling 15. By bringing the ferrules 1 and 1 ′ ends of the optical fiber fixtures 3 and 3 ′ into contact with each other by the pressing force of the springs 17 that are screwed and arranged between the coupling nuts 16 and the ferrule support 2, The fibers 11 and 11 ′ are optically connected to each other.

  The sleeve 14 has a cylindrical shape in which an inner hole 14a is bent at a substantially central portion 14b, and an incident beam can be incident on the multimode optical fiber 11 ′ from the single mode optical fiber 11 obliquely with respect to the axial direction. It becomes.

  Next, FIG. 1B shows an enlarged view of the state in which the ferrules 1 and 1 ′ and the optical fibers 11 and 11 ′ in FIG.

  Normally, the ferrule 1 on the incident side has a shaft hole 1a at a substantially central position of the outer peripheral portion, and a single mode optical fiber 11 is bonded and fixed to the shaft hole 1a. For example, a core of a pair of optical fibers In order to decenter the center positions of the output side ferrule 1 ′, a shaft hole 1a ′ is provided at a position decentered from the center of the outer peripheral portion of the output side ferrule 1 ′, and a multimode optical fiber 11 ′ is bonded and fixed to the shaft hole 1a ′. The front end surfaces of the ferrules 1 and 1 ′ are fixed in the inner hole 14 a of the sleeve 14.

  Therefore, the center position 11b of the core 11a of the single mode optical fiber 11 and the center position 11b ′ of the core 11a ′ of the multimode optical fiber 11 ′ are eccentric and incident obliquely with respect to the axial direction. The light that has passed through the optical fiber 11 is incident on the central portion of the multi-mode optical fiber 11 ′ after removing the low-refractive-index “recessed” portion, causing anomalous dispersion of the mode and preventing the signal from interfering. Therefore, it is possible to transmit efficiently.

  FIG. 2 is a conceptual diagram showing the incident direction when light enters the multimode optical fiber 11 ′.

  The eccentric direction of the center position 11b ′ of the core 11a ′ of the incident beam incident position 18a is the X axis, the optical fiber axial direction is the Z axis, the direction perpendicular to the X axis and the Z axis is the Y axis, and the Y axis and the Z axis are When the axes shifted by the amount of eccentricity δ whose core positions are eccentric from each other are defined as the Y ′ axis and the Z ′ axis, respectively, the incident beam 18 is placed in the plane formed by the Y ′ axis and the Z ′ axis. Incident at an angle of ψ with respect to the axis.

  In the optical connector 10 of the present invention, the relative eccentricity δ of the center position 11b ′ of the core 11a ′ is decentered within the range of 10 to 25 μm, and the incidence of the optical fiber is within the plane formed by the Y ′ axis and the Z ′ axis. The beam 18 is connected by tilting the angle ψ with respect to the axis of the optical fiber within a range of 3 to 25 °.

  Here, the relative eccentricity δ of the center position 11b ′ of the core 11a ′ is in the range of 10 to 25 μm. If the relative eccentricity δ is less than 10 μm, the eccentric effect cannot be exhibited, and the multimode optical fiber 11 ′. In the central portion of the optical fiber, light enters a portion such as a “dent” having a low refractive index, and abnormal dispersion of modes occurs. When the thickness exceeds 25 μm, the core diameter of the multimode optical fiber is 50 μm or 62. Since the incident light deviates from the core part because of 5 μm, the light is not properly propagated, so that it is within the range of 10 to 25 μm. A more desirable effect can be obtained by adjusting the eccentricity δ to 15 to 20 μm within this range.

  Further, the angle ψ is set within the range of 3 to 25 °. If the angle ψ is less than 3 °, the effect of shifting the angle cannot be exerted, and the “dent” having a low refractive index at the central portion of the multimode optical fiber 11 ′. As a result, light is incident on such a portion, resulting in abnormal dispersion of modes, and if the angle exceeds 25 °, the incident angle is too large and light incident on the core portion escapes to the cladding portion. In order to prevent the light from being properly transmitted, the angle is set in the range of 3 to 25 °. If the angle ψ is adjusted to 5 to 15 ° within this range, a more preferable effect can be obtained.

  Thus, in the optical connector 10 for connecting the end faces of the pair of optical fibers, the center position 11b of the core 11a of the pair of single mode optical fibers 11 is relatively eccentric by the distance of the eccentric amount δ, and By connecting the incident beams 18 of a pair of optical fibers inclined at an angle of ψ, the optical signals are propagated in a spiral manner in the core 11a ′ of the graded index multimode optical fiber as shown in FIG. As a result, transmission is performed by removing a hollow portion having a low refractive index in the central portion of the multi-mode optical fiber 11 ′, so that anomalous dispersion of modes does not occur, and the signal interferes. Without this, optical transmission over a distance of 550 m or more, in which a high-speed signal is defined, becomes possible.

  In the above description, the single mode optical fiber 11 is fixed to the center of the ferrule 1 and the multimode optical fiber 11 ′ is eccentrically fixed to the ferrule 1 ′. However, the present invention is not limited to this. As long as the center positions 11b and 11b ′ of the cores of the fiber 11 and the multimode optical fiber 11 ′ are decentered from each other, the effects of the present invention can be achieved with any configuration.

  The ferrules 1 and 1 'of the present invention may be made of ceramics such as zirconia, alumina and glass, metals such as stainless steel, plastics such as LCP, PPS, PES and PEI, or a mixed material thereof.

  The structure of the sleeve 14 may be either a split sleeve with a slit in the longitudinal direction or a precision sleeve without a slit, and the material may be any of zirconia, phosphor bronze, and plastic. It can be machined or injection molded like plastic. Among these, plastic injection molding is particularly desirable because a complicated shape can be manufactured at a relatively low cost depending on the shape of the mold.

  Here, the experiment was conducted by the following method.

  A ferrule made of zirconia ceramics is prepared with an outer diameter D = diameter 2.5 mm, a length L = 10.5 mm, a through hole d = diameter 0.126 mm, and a single mode optical fiber 11 is bonded and fixed to the ferrule 1 on the incident side. Then, the multi-mode optical fiber 11 ′ was bonded and fixed to the output-side ferrule 1 ′, and the end faces of the pair of optical fibers were connected to each other with the center positions 11b and 11b ′ of the optical fiber being eccentric.

  The eccentricity δ was set to 5, 9, 10, 15, 20, 25, and 30 μm as examples, and 0 μm as a comparative example.

  In addition, the angle ψ is set to 2, 3, 10, 20, 25, 26 ° as an example, and set to 0 ° as a comparative example, and the length of the optical fiber is increased every 50 m in each combination to increase the transmission distance. Was measured.

  The multimode optical fiber used here has a core diameter of 62.5 μm and a cladding diameter of 125 μm.

  As shown in FIG. 4, an optical signal is emitted from the E / O converter 22 of the transceiver 21 so that the wavelength is 1310 nm and the transmission speed is 10 Gbit / second, and the measurement method is connected to the single mode optical fiber 11. The multimode optical fiber 11 ′ for measurement was connected via the optical connector 10 of the present invention. The light transmitted through the multimode optical fiber 11 ′ was received by the O / E converter 25 of the receiver 24 through a general optical connector and converted into an electric signal to confirm whether a correct signal was transmitted.

Table 1 shows the results describing the maximum length of transmission of the correct signal.

  When the eccentricity δ of the comparative example was 0 μm, the transmission distance was 0 m at any angle ψ.

  Further, even when the angle ψ of the comparative example was 0 °, the transmission distance did not reach 100 m.

  In contrast, in the embodiment of the present invention, a transmission distance of 100 m or more can be obtained, and further, the transmission distance becomes 550 m or more when the eccentricity δ is in the range of 10 to 25 μm and the angle ψ is in the range of 3 to 25 °. It ’s a good value.

  In particular, when the eccentricity δ is 15 to 20 μm and the angle is 5 to 15 °, a higher transmission distance of 750 m can be obtained.

  As described above, in the optical connector for connecting the end faces of the pair of optical fibers, the center position of the core of the pair of optical fibers is relatively decentered, and the incident beam wave of the pair of optical fibers is inclined and incident. By connecting, the light that has passed through the single-mode optical fiber is incident on the central portion of the multi-mode optical fiber after removing the low refractive index indentation, and abnormal dispersion of the mode does not occur. It can be seen that the signal was transmitted efficiently without interference.

(A) is sectional drawing which shows the optical connector of this invention, (b) is the elements on larger scale. It is a conceptual diagram which shows an incident direction in case light injects into the multimode optical fiber of this invention. It is a conceptual diagram which shows the propagation state of the optical signal in the core of the multimode optical fiber of this invention. It is a conceptual diagram which shows the measuring method in an Example. (A) is a graph showing the refractive index distribution of an ideal multimode optical fiber, (b) is a graph showing the refractive index distribution of an actual multimode optical fiber. It is sectional drawing which shows the conventional optical connector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1 ': Ferrule 1a, 1a': Shaft hole 2: Ferrule support body 2a: Recess 2b: Through-hole 3: Optical fiber fixture 10: Optical connector 11: Single mode optical fiber 11a: Core 11b: Center position 11 ' : Multimode optical fiber 11a ': Core 11b': Center position 13: Adhesive 14: Sleeve 14a: Inner hole 14b: Center part 15: Adapter coupling 16: Adapter coupling nut 17: Spring 18: Incident beams 31, 31 ': Ferrule 31a, 31a ': shaft hole 32: ferrule support 32a: recess 32b: through hole 33: optical fiber fixture 40: optical connector 41, 41': single mode optical fiber 43: adhesive 44: sleeve 45: adapter coupling 46: Adapter coupling nut 47: Spring

Claims (3)

In the optical connector for connecting the end faces of a pair of optical fibers , one of which is a single mode optical fiber and the other is a multimode optical fiber, the center position of the core of the pair of optical fibers is within a range of 10 to 25 μm. By making them abut so as to be eccentric with each other and making the incident beam from one optical fiber tilt with respect to the axis of the other optical fiber within a range of 3 to 25 ° , both are optically incident. When the eccentric direction of the center position of the core is the X axis, the axial direction of the optical fiber is the Z axis, and the direction perpendicular to the X axis and the Z axis is the Y axis, the Y axis and the Z axis are When the axes shifted by the amount of eccentricity where the center positions of the cores are offset from each other are defined as the Y ′ axis and the Z ′ axis, the incident beam is within the plane formed by the Y ′ axis and the Z ′ axis. A featured optical connector. 2. The optical connector according to claim 1, wherein the pair of optical fibers are brought into contact with each other so that a center position of the core is eccentric within a range of 15 to 20 [mu] m . The ferrule holding at least one of the end portions of the optical fiber eccentric from the center position of the ferrule is inserted into a cylindrical sleeve having an inner hole bent at a substantially central portion. Item 3. The optical connector according to Item 1 or 2.

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