The present invention relates to a cleaning tool for an optical connector which cleans an optical connector for connecting optical fibers.
As optical communication or optical measurement using light has developed remarkably in recent years, the loss at the connecting portion of an optical connector for connecting optical fibers poses a problem.
In such an optical connector, optical fibers are generally connected to oppose each other. In this case, if the connecting end face of the optical connector is soiled or a substance such as fats and oils or dust attaches to it, the insertion loss of the optical fiber is increased to decrease the reflection attenuation amount, and an optical signal cannot be transmitted correctly. For this reason, the connecting end face of the optical connector must be cleaned periodically or when necessary to remove the soil or attaching substance.
Conventionally, when the connecting end faces of optical connectors are to be cleaned, the operator cleans the end faces by wiping them with a cleaning tool, e.g., a cleaning sheet or paper impregnated with ethyl alcohol, or spraying nitrogen gas to them. In the wiping cleaning operation using a cleaning sheet or paper impregnated with alcohol, the amount of alcohol to be used and the wiping degree change depending on the operator who performs cleaning, and the cleaning effect tends to vary. Since alcohol tends to catch fire easily, it must be handled and stored with sufficient care.
In view of this, a dry cleaning tool has recently been proposed to replace the wet cleaning tool described above. According to the dry cleaning tool, a cleaning cloth formed into a tape-like shape is urged and rubbed against a ferrule end face (connecting end face), thereby removing an attaching substance, e.g., a soil, dust, or oils and fats, attaching to the ferrule end face, particularly the coupling surface (end face) of an optical fiber which forms one plane together with the connecting end face.
FIGS. 9 and 10 show a dry cleaning tool for an optical connector previously filed by the present applicant. This cleaning tool 1 has a thin box-like case 2, and the structure shown in FIG. 10 is loaded in the case 2. This structure has a supply pulley 4 on which a tape-like cleaning sheet 3 is wound, a take-up pulley 5 for taking up the cleaning sheet 3, and a ratchet mechanism (not shown) for rotating the supply pulley 4 in only a predetermined direction (take-up direction) to prevent the cleaning sheet 3 from becoming loose.
Part of one side wall 2a along the long side of the case 2 has an open window 6 for exposing the cleaning sheet 3 to the outside, and a shutter 7 for opening/closing the open window 6. A rotary drive mechanism (not shown) for driving the supply pulley 4, a tape feed grip 8 for driving the rotary drive mechanism, and a pad 9 for receiving and supporting that sheet portion of the cleaning sheet 3 which is exposed from the open window 6 are built in the case 2.
FIG. 11 shows an example of an optical connector 10 to be cleaned by the cleaning tool 1 shown in FIGS. 9 and 10. This optical connector 10 has a plug body 11 and a ferrule 12 built in the plug body 11 and with a front end face (connecting end face) projecting from the front end face of the plug body 11. An optical fiber 13 is arranged at the center of the ferrule 12. While the optical fiber 13 is inserted in the ferrule 12, it is fixed with an adhesive or the like such that its coupling surface 13a as the distal end face forms one plane together with the connecting end face of the ferrule 12. In this state, the connecting end face of the ferrule 12 and the coupling surface 13a of the optical fiber 13 are mirror-surface polished.
When optical connectors 10 with this structure are employed, the coupling surfaces 13a of the optical fibers 13 are brought into contact with each other by engagement of an engaging portion 14 formed on the side surface of one plug body 11 and an engaging portion formed on the plug body of the mating optical connector. Hence, the plug bodies 11 are coupled to each other and an optical signal is transmitted. In this case, if the coupling surfaces 13a are soiled, or a substance such as dust or oils and fats attaches to them, light from the optical fiber 13 is absorbed to increase the insertion loss of the optical connectors 10, thereby decreasing the reflection attenuation amount. Consequently, the optical signal cannot be transmitted correctly.
When the connecting end face of the ferrule 12 in the optical connector 10 and the coupling surface 13a of the optical fiber 13 are to be cleaned by the cleaning tool 1, first, the user grips the tape feed grip 8. Then, the shutter 7 opens interlocked with the tape feed grip 8, to expose the cleaning sheet 3 to the outside from the open window 6. Also, the rotary drive mechanism (not shown) is driven to rotate the take-up pulley 5 in the take-up direction. Therefore, the supply pulley 4 feeds a predetermined amount of cleaning sheet 3, so that a new, unused sheet portion is supplied to the open window 6. In this state, when the connecting end face of the ferrule 12 of the optical connector 10 is urged and rubbed against the surface of the cleaning sheet 3 exposed from the open window 6, the substance such as a soil, dust, or oils and fats attaching to the coupling surface 13a of the optical fiber 13 is removed, thus cleaning the coupling surface 13a. After cleaning, when the user releases the holding state of the tape feed grip 8, the tape feed grip 8 is restored to the initial position by the force of a spring incorporated in the case 2, and the shutter 7 closes the open window 6.
With the conventional cleaning tool 1 described above, although the connecting end face of the ferrule 12 and the coupling surface 13a of the optical fiber 13 can be cleaned well by removing the attaching substance or soil from them, the side surface of the ferrule 12 cannot be cleaned at all. If a substance such as dust attaches to the side surface of the ferrule 12, or the optical connector 10 in a soiled state is mounted in a device or the like, the insertion loss is increased due to the attaching substance or soil on the side surface of the ferrule 12, and the reflection attenuation amount decreases. As a result, an optical signal cannot be transmitted correctly.
This will be described in more detail by means of a practical example. As shown in FIGS. 12 or 13, when sebum, dust, or a polishing liquid (containing diamond abrasive grains, SiO2 crystals, alumina, or the like) attaches to the side surface of the ferrule 12, the optical fibers 13 to be connected are not connected such that their coupling surfaces do not oppose each other correctly, but the optical axes of the two optical fibers are tilted. Then, as shown in FIG. 14, the insertion loss increases in accordance with the degree of the tilt of the optical axes. This insertion loss is correlated not only to the tilt (angular shift) of the optical axes but also to the offset (misalignment) and gap. When an angular shift of 1xc2x0 occurs, off-axis occurs simultaneously. Therefore, the insertion loss is the sum of the angular shift and misalignment. With dust or the like attaching to the side surface of the ferrule, when this ferrule is to be connected with another ferrule, if an angular shift occurs between the two ferrules, this leads to a very large influence. For example, with a misalignment of 0.5 mm, the connection loss becomes 0.1 dB. Generally, a connection loss at one connection point must be 0.2 dB or less. If misalignment occurs, as described above, an angular shift also occurs, and the connection loss at this time becomes 0.1 dB. Therefore, the sum of the connection loss becomes 0.2 dB, which is larger than the general requirement. Referring to FIGS. 12 and 13, reference numeral 1 denotes a split sleeve; 2, an adapter sleeve holder; 3, a ferrule; 4, dust; 5, a ferrule to which the dust attaches; 6, a precision sleeve; 7, dust; 8, a lens; and 9, a display such as a CRT.
The present invention has been made to solve the conventional problems described above, and has as its object to provide an optical connector cleaning tool which can reliably clean the side surface of a ferrule so as to decrease the connection loss caused by dust or the like at the optical connector portion, has a simple structure and a smaller number of components, and is inexpensive and easy to use.
It is another object of the present invention to provide an optical connector cleaning tool which improves the operation efficiency for the side surface of a ferrule and has a stable cleaning ability.
In order to achieve the above objects, according to the present invention, there is provided a cleaning tool for an optical connector, comprising a cylindrical cleaner and a holding member for holding a proximal portion of the cleaner, the cleaner having a main body with a ferrule insertion hole extending from a ferrule insertion port at a distal end face thereof toward the proximal end of the cleaner and having an inner diameter substantially the same as an outer diameter of a ferrule, and the ferrule insertion hole being surrounded by a rough surface so as to clean an outer surface of the ferrule which is to be inserted.
In this case, the main body of the cleaner is made of either one of ultra-fine fiber, urethane, and rubber.
The inner wall surface of the main body of the cleaner and that of the plug form rough surfaces so that they can clean the end faces of the ferrule and optical fiber and the side surface (more precisely the capillary portion) of the ferrule.
These rough surfaces are formed by processing ultra-fine fiber, urethane, or rubber.