Optical waveguides – Accessories – Attenuator
Reexamination Certificate
1997-12-03
2001-02-06
Healy, Brian (Department: 2874)
Optical waveguides
Accessories
Attenuator
C385S037000
Reexamination Certificate
active
06185358
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C § 119 from an application entitled OPTICAL ATTENUATOR AND METHOD OF MANUFACTURING SAME earlier filed in the Korean Industrial Property Office on the 3
rd
day of December 1996, and there duly assigned Serial No. 96-61400 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an optical attenuators and processes for manufacturing optical attenuators, and, more particularly, to an optical attenuator and a process of manufacturing optical attenuators able to attenuate incident light of an optical fiber by varying a refractive index of a core layer of the optical fiber.
2. Description of the Related Art
Generally, when processing an optical communication signal carried by an optical transmission network, an optical signal exhibiting some degree of strength within a light receiving range of an optical receiver module should be received. If the strength of the optical signal exceeds the range of capacity for the light receiver, an error is likely to occur in the optical receiver module that will cause a serious problem in an operating lifetime. To solve theses disadvantages, an optical attenuator has been used.
Optical attenuators may be classified as either a plug-in type or an in-line type, as are discussed in greater detail in conjunction with attenuators illustrated by
FIGS. 1 and 2
of this application. Examples of earlier efforts in the art are exemplified by way of illustration, by the Ruggedized Grated Optical Fiber of Jack E. Goodman, et alii, U.S. Pat. No. 4,593,969; the Optical Waveguide Embedded Transverse Spatial Mode Discrimination Filter of William H. Glenn, et alii, U.S. Pat. No. 5,048,913; the Optical Fiber Laser Or Amplifier Including High Reflectivity Gratings of Stephen G. Grubb, U.S. Pat. No. 5,323,404; and the Optical Fiber Package of William M. MacDonald, et alii, U.S. Pat. No. 5,367,589; and the techniques for creating gratings mentioned in Bragg Grating Made In Optical Waveguide of Elias Snitzer, et alii, U.S. Pat. No. 5,351,321, in Method Of Fabricating Bragg Gratings Using A Silica Glass Phase Grating Mask And Mask Used By Same of Kenneth O. Hill, et alii, U.S. Pat. No. 5,367,588, the Incubated Bragg Gratings In Waveguides of Kevin C. Byron, et alii, U.S. Pat. No. 5,574,810, the Optical Waveguide With Diffraction Grating And Method Of Forming The Same, of Hans Bruesselbach, U.S. Pat. No. 5,604,829, and the Method Of Detecting And/Or Measuring Physical Magnitudes using a Distribution Sensor of And/oe Tardy, U.S. Pat. No. 5,684,297.
Both plug-in and an in-line types of attenuators often seek to attenuate the strength of incident light traveling between two adjoining lengths of optical fiber by inserting a thin film optical filter into a ferrule or a sleeve. In order to attenuate the incident light by reflecting or absorbing the optical signal, the thin film optical filter is coated to a multilayer structure by using various kinds of metal elements and finally processes its both surfaces by non-reflection coating so as to maintain a non-reflectance of 99.8% or more.
With conventional designs of plug-in type of optical attenuators, however, because it has been difficult to process the thin film filter to obtain a non-reflective coating that provides non-reflectance of 99.8% or more, any optical signal that is reflected in a very high speed optical transmission network of 2.5 Giga-bits per second or more backwardly enters the interior of the optical fiber. Consequently, an error in the optical signal is likely to occur. Moreover, since the thin film filter bearing the thin film coating and the non-reflective coating may easily become separated due to temperature and humidity, the characteristics of the optical signal may vary according to the wavelength of the optical signals. Furthermore, since the optical fiber is cut at an angle of eight degrees and the thin film filter is fixed between the ferrules in order to attenuate the incident light of the optical fiber, even though no contact is made by external components and the thin film filter during coupling of the optical connector, additional components must be used in order to connect the optical adaptor to the optical distribution box. These additional optical components increase the cost of a product and make it exceedingly difficult to pack the optical connectors in a dense array in the optical distribution box.
Additionally, with conventional optical in-line attenuators, since it is difficult to obtain a thin film filter with the non-reflection coating providing a non-reflectance of 99.8% or more, the optical signal reflected in the very high speed optical transmission network of 2.5 Gbps or more is reflected backwardly into the interior of the optical fiber and causes errors in the optical signal. Moreover, due to separation of the thin film filter bearing the thin film and non-reflection coating due to temperature and humidity, the characteristics of the optical signal tend to vary according to wavelength. Furthermore, since the middle portion of the optical cable is cut and the thin film filter inserted between the adjoining end surfaces in order to attenuate the incident light of the optical fiber, the tensile strength of the optical cable is reduced and it is difficult to process and manage the presence of any additional optical cable within the optical distribution box.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved optical attenuator and process for manufacturing optical attenuators.
It is another object to provide an optical attenuator and process for manufacturing optical attenuators that are able to attenuate the incident light of an optical fiber without using an additional thin film filter.
It is still another object to provide an optical attenuator and process for manufacturing optical attenuators that can attenuate the incident light of an optical fiber by varying a refractive index of a core layer of the optical fiber.
It is yet another object to provide an optical attenuator and process for manufacturing optical attenuators that can easily process and manage an extra optical cable within an optical distribution box.
It is still yet another object to provide an optical attenuator and process for manufacturing optical attenuators that does not vary in characteristic even if after a long period of non-use.
It is a further object to provide an optical attenuator and process for manufacturing optical attenuators that can minimize the size of optical attenuators.
It is also an object to provide processes for fabricating optical attenuators in situ within an unbroken length of an optical fiber, and to provide unbroken optical fibers containing optical attenuators formed in situ.
According to one aspect of the present invention, an optical attenuator includes an optical fiber installed in a tube able to shield the optical filter from influences of changes in external circumstances, and at least one grating formed in the optical fiber, for breaking total reflection conditions due to varying refractive indices of a core layer and a clad layer of the optical fiber in order to attenuate incident light during optical transmission.
According to another aspect of the present invention, a process for manufacturing an optical attenuator includes the steps of emitting an optical source of an excimer laser to an optical fiber by a phase mask process in order to break total reflection conditions by varying refractive indices of a core layer and a clad layer of the optical fiber, and forming a plurality of first gratings at intervals within the range of 500 nm~600 nm in order to attenuate the incident light of the optical fiber and to reflect or pass the light of other wavelengths.
REFERENCES:
patent: 4557557 (1985-12-01), Gleason et al.
patent: 4593969 (1986-06-01), Goodman et al.
patent: 4749248 (1988-06-01), Aberson, Jr. et al.
patent: 4884859 (1989-12-01), Yamamoto et al.
p
Bushnell , Esq. Robert E.
Healy Brian
Samsung Electronics Co,. Ltd.
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