Optical waveguides – With disengagable mechanical connector – Structure surrounding optical fiber-to-fiber connection
Patent
1996-11-14
1997-10-07
Ngo, John
Optical waveguides
With disengagable mechanical connector
Structure surrounding optical fiber-to-fiber connection
385 54, 385 80, 385 65, G02B 638
Patent
active
056756810
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention generally relates to optic fiber signal transmission equipment.
More in particular, this invention concerns a multifiber connector device for optic fiber cables.
Different types of connectors are known and used for the realization of connections among optic fiber cables.
BACKGROUND ART
A first example of a typical multifiber connector, indicated as a whole with 10, is shown in FIG. 1.
Connector 10 includes two coupling parts indicated with 13 and 13', respectively.
Inside part 13 of connector 10, a plurality of optic fibers 12 is housed and comes out from the end of an optic fiber tape 11.
Similarly, inside part 13' of connector 10, a plurality-of optic fibers is housed and comes out from the end of an optic fiber tape 11'.
On the front surface 15 of part 13 of connector 10, two guide holes 14 are obtained.
Holes 14 are placed aside fibers 12 with longitudinal axis parallel to the axis of the fibers themselves.
The front surface 15 of part 13' shows two pins 16.
Pins 16 are arranged aside the optic fibers 12' with longitudinal axis parallel to the axis of the fibers 12' and in a position coinciding to holes 14.
Connector 10 includes a clamping spring 17 to fix the two parts 13 and 13'.
Through insertion of the two pins 16 inside the guide holes 14 optic fibers 12 alignment with optic fibers 12' is obtained and, consequently, the optic connection of cable 11 and cable 11 '.
Due to the action of the clamp 17, the two front surfaces 15 and 15' of the two parts 13 and 13' reciprocally adhere.
A serious problem associated to similar connectors is due to the fact that they do not allow satisfactory alignment of optic fibers abutted on the two parts 13 and 13' of Connector 10.
In connector 10 of FIG. 1 the correct alignment of fiber is simply determined by the coupling between pins 16 and holes 14.
This mechanical coupling is absolutely insufficient to align optic fibers with the required very high accuracy.
To this purpose, it must be considered that the active core thickness of an ordinary optic fiber is of 8 micron only.
Being the transmission coefficient between two coupled fibers proportional to the area of the contact front surface of fibers themselves (hence, inversely proportional to the square of distance between axis of fibers) we can easily understand how a minimum misalignment among fibers (in the range of micron fractions) can lead to unacceptable attenuation of the signal.
To try to minimize this serious disadvantage, pins 16 and holes 14 are made according to very high accuracy construction techniques, involving an increase of realization costs and difficult construction processes.
Also, to allow the insertion of pins 16 inside guide holes 14, the external diameter of pins 16 must be slightly lower than the internal section of guide holes 14.
The backlash associated to this small size difference is often sufficient to impair the good quality of the optic connection offered by connector 10.
The clamping action of the spring 17, required for the correct union of the two front surfaces 15 and 15' can distort the two parts 13 and 13' of connector 10, modifying the possible correct alignment of optic fibers.
To try to minimize these disadvantages, alternative solutions have been proposed where said holes 14 are replaced by slides made on the connector sides.
However, also in this case, the associated backlash between pins and slides is such to impair the good quality of the optic connection offered by the connector.
In summary, the optic connection offered by connectors of this type is characterized by attenuation values always rather high (1 dB approx.) and by the poor repetition capability of the signal attenuation value during the different insertions.
U.S. Pat. No. 4,898,449 discloses a connector including two coupling elements in each of which end parts light conducting fibers are secured in such a manner that the centers of their end faces are situated on one line.
The connector further comprises a connector housing for receiving the two coupling el
REFERENCES:
patent: 4898449 (1990-02-01), Vroomen et al.
patent: 4993800 (1991-02-01), Shibata
patent: 5600747 (1997-02-01), Yamakawa et al.
Jacobs et al. (1988) Optical Communication (ECOC 88), Part 1, pp. 585-588.
Chiaretti Guido
Parafioriti Giacomo
Italtel SpA
Ngo John
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