Optical waveguides – Accessories – Attenuator
Reexamination Certificate
1998-04-28
2001-10-16
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Accessories
Attenuator
C385S033000, C385S025000, C385S018000, C385S047000
Reexamination Certificate
active
06304709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a variable optical attenuator for use in optical communication and to an optical signal source for wavelength-multiplexed optical transmission systems.
2. Description of the Related Art
Conventionally, there has been known a variable optical attenuator having a structure in which the distance between ferrules opposed each other is changed to thereby vary optical coupling efficiency between the ferrules (see Japanese Unexamined Patent Application No. 8-94843). Also known are a variable optical attenuator having a structure utilizing the dependency of the intensity of a damped wave at the interface between different types of optical transmission mediums on the light incidence angle (Japanese Unexamined Patent Application No. 57-122403), that having a structure in which a disk-shaped optical filter having an attenuation factor varying in a sector manner is inserted into an optical path (Japanese Unexamined Patent Application No. 3-257414) and that having a structure in which two optical fibers arranged in parallel are optically coupled through a reflection mirror and an attenuation plate is inserted between the optical fiber and the reflection mirror (U.S. Pat. No. 5,226,104).
Conventional variable optical attenuators are provided with mechanisms for adjusting optical attenuation at positions perpendicular to the optical axes of optical fibers, respectively. If a plurality of variable optical attenuators are mounted on, for example, the panel of an apparatus, it is necessary to provide clearances between adjacent variable optical attenuators for operating the adjustment mechanism. This makes it difficult to realize high-density mounting. For the same reason, once the variable optical attenuators are mounted on the panel of the apparatus, it is impossible to adjust optical attenuation from the outside of the panel. Due to this, maintenance becomes difficult.
In case of a wavelength-multiplexed optical transmission system for transmitting a light beam after composing a plurality of signal lights having different wavelengths, in particular, there is only a narrow space in the panel. For that reason, it is required to easily mount and adjust the variable optical attenuators. It is also required to accurately keep output levels of the light beams of different wavelengths coincide with one another.
SUMMARY OF THE INVENTION
It is therefore an object of a variable optical attenuator and an optical signal source for wavelength-multiplexed optical transmission systems according to the present invention to realize high-density mounting. It is another object of the present invention to make it possible to easily adjust optical attenuation even after mounting the attenuator on, for example, the panel of the apparatus.
A variable optical attenuator according to the present invention comprises: a first optical fiber; a reflection mirror reflecting a light beam emitted from an end face of the first optical fiber; a second optical fiber arranged parallel to the first optical fiber, on which second optical fiber the emitted light beam reflected by the reflection mirror is incident; and position adjustment means for adjusting a distance between the reflection mirror and the end face.
The variable optical attenuator according to the present invention further comprises beam converging means arranged between the end face and the reflection mirror, for converging the light beam emitted from the end face onto the reflection mirror. The position adjustment means comprises a cylinder housing the reflection mirror and having screws at an outer diameter thereof; and a box-shaped member housing the first optical fiber and the second optical fiber and having screws for fitting the cylinder into an inner diameter thereof. The distance is adjusted by rotating the cylinder.
Two optical fibers and the lens are fixed to the box-shaped member. The relative positions of these elements are not changed. The reflection mirror is fixed to the cylinder. The cylinder is inserted into a hole provided in the box-shaped member. The cylinder is rotatable within the hole. In this case, if the structure is such that the cylinder is fitted into the hole of the box-shaped member with screws, the distance between the reflection mirror and the optical fibers is changed by the rotation of the cylinder. Owing to this, the optical coupling amount between the optical fibers, i.e., optical attenuation is changed.
A variable optical attenuator according to the present invention comprises: a first optical fiber; a reflection mirror reflecting a light beam emitted from an end face of the first optical fiber; a second optical fiber arranged parallel to the first optical fiber, on which second optical fiber the emitted light bean reflected by the reflection mirror is incident. With the structure stated above, the reflection mirror includes a reflection film having a reflection factor varying according to a light incidence position. The variable optical attenuator further comprise irradiation position adjustment means for changing a position at which the light beam emitted from the end face is irradiated with the reflection mirror.
The variable optical attenuator according to the present invention further comprises beam converging means, arranged between the end face and the reflection mirror, for converging the light beam emitted from the end face onto the reflection mirror. The reflection mirror includes a reflection film formed such that the reflection factor is gradually changed in a sector manner. The irradiation position adjustment means includes a reflection mirror rotation unit for rotating the reflection mirror. By the rotation of the reflection mirror with the reflection mirror rotation unit, a position at which the light beam is irradiated onto the reflection film can be changed. If the rotation axis of the cylinder is set to be shifted relative to the optical axes of the optical fibers and the reflection factor of the reflection mirror is gradually changed in a sector manner, then incidence points of light beams emitted from the optical fibers on the reflection mirror are changed with the rotation of the cylinder and therefore optical reflection amounts are changed. Thus, it is possible to change optical attenuation between the optical fibers.
A variable optical attenuator according to the present invention further comprises a half mirror arranged between the beam converging means and the reflection mirror and reflecting part of the light beam to thereby output a monitor light beam; and a photo detector receiving the monitor light beam.
A variable optical attenuator according to the present invention comprises a first optical fiber; a reflection mirror reflecting a light beam emitted from an end face of the first optical fiber; a second optical fiber arranged parallel to the first optical fiber, on which second optical fiber the emitted light beam reflected by the reflection mirror is incident; and incidence angle adjustment means for adjusting an incidence angle of the light beam at which the light beam is incident on the reflection mirror. The variable optical attenuator according to the present invention further comprises beam converging means, arranged between the end face and the reflection mirror, for converging the light beam emitted from the end face onto the reflection mirror. Here, the incidence angle adjustment means comprises a cylinder housing the reflection mirror; and a box-shaped body housing the first optical fiber and the second optical fiber and housing the cylinder. The reflection mirror is housed in the cylinder so as not to be perpendicular to a center line of an inner diameter. The angle is adjusted by rotating the cylinder inside the box-shaped body.
The cylinder, to which the reflection mirror is fixed, has a wedge-shaped cross-section. If the center line of the hole provided in the box-shaped member is inclined toward optical axes of the two optical fibers, the incidence angle on the reflection mirror fixed to the cyli
McGuireWoods LLP
NEC Corporation
Palmer Phan T. H.
LandOfFree
Variable optical attenuator and wavelength-multiplexed... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Variable optical attenuator and wavelength-multiplexed..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Variable optical attenuator and wavelength-multiplexed... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2611226