Optical waveguides – Optical fiber waveguide with cladding
Reexamination Certificate
2002-12-17
2004-09-14
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Optical fiber waveguide with cladding
C385S142000, C501S037000
Reexamination Certificate
active
06792187
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to Ca—Al—Si oxide glasses and their use in optical components, such as optical fibers and planar waveguides.
BACKGROUND OF THE INVENTION
Optical fiber for long distance communications has reached a remarkable state of perfection. For instance, single mode fibers having loss of about 0.20 dB/km are routinely being produced. Nevertheless, there is still great interest in further reducing the signal loss, since even a reduction as small as 0.01 dB/km can translate into a significant increase in the permitted distance between repeaters. This in turn can translate into a significant difference in system cost, especially for transmission systems such as transoceanic fiber optic systems that by necessity have to employ highly complex and thus costly repeaters.
Factors affecting the light transmission loss of optical fibers include: intrinsic losses resulting from materials constituting the optical fibers, such as Rayleigh scattering, ultraviolet and infrared absorption loss; scattering losses due to fiber structure imperfection and glass flaws, such as scattering by irregularities of the interface of a core and a cladding, strias and bubbles; and absorption loss by impurities that remain in fibers, such as absorption by iron and other transition metals, or absorption by vibration of a hydroxyl group. Imperfection losses and absorption losses can be alleviated in many respects by controlling process parameters.
Intrinsic losses resulting from the materials can only be overcome by the development of new glasses that achieve the desired characteristics for fiber materials. The intrinsic loss in the wavelength region that can be used for transmission of light (i.e., between ultraviolet and infrared absorption edges of a glass) is controlled mainly by Rayleigh scattering from frozen-in density and composition fluctuations in the glass. The length scale of such fluctuations is smaller than the wavelength of light. Since these types of scattering loss are intrinsic to a glass composition, it constitutes the absolute theoretical lower limit of transmission loss that can be obtained from a dry high-purity optical fiber.
Optical fibers from a silica glass composition have become preeminent in the communication field because of advantages such as cost and relative facile processing. However, optical fibers from a silica composition have certain shortcomings which impose limitations on the use thereof. For instance, silica-based optical fibers can transmit light over the limited wavelength range of about 200-2000 nm and have the lowest optical loss of about 0.2 dB/km at a wavelength of 1550 nm.
Low intrinsic scattering losses, as low as fifty percent of that of pure silicon dioxide, have been reported for a number of multi-component oxide glasses in Na—Al-silicate, Na—Mg-silicate, Na—Ca-silicate, Ba—Ga-germanate. However, many of these multi-component glasses suffer from the lack of stability against crystallization. Moreover, the presence of alkali in these compositions makes it impossible to dry and purify these materials at high temperatures with chlorine gas due to the formation of alkali chlorides crystals.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to an optical component for a telecommunication system containing a glass light conducting material that includes, in mole percent: SiO
2
present in an amount of about 6 to about 60 percent, Ga
2
O
3
, Al
2
O
3
, or a combination thereof present in an amount of about 12 to about 31 percent, and CaO present in an amount of about 20 to about 65 percent.
Another aspect of the present invention relates to a glass having a composition that includes, in mole percent:
(a) SiO
2
present in an amount of about 6 to 13.5 percent or 29 to about 60 percent, Ga
2
O
3
, Al
2
O
3
, or a combination thereof present in an amount of about 12 to about 31 percent, and CaO present in an amount of about 20 to about 65 percent; or
(b) SiO
2
present in an amount of about 6 to about 60 percent, Ga
2
O
3
, Al
2
O
3
, or a combination thereof present in an amount of about 12 to 13.5 percent or 27.5 to about 31 percent, and CaO present in an amount of about 20 to about 65 percent; or
(c) SiO
2
present in an amount of about 6 to about 60 percent, Ga
2
O
3
, Al
2
O
3
, or a combination thereof present in an amount of about 12 to about 31 percent, and CaO present in an amount of about 20 up to 49.5 percent.
Yet another aspect of the present invention relates to a method of transmitting an optic signal that includes: passing an optic signal into one end of an optical component of the present invention under conditions effective to transmit the signal to an opposite end of the optical component, wherein the signal loss from the one end to the opposite end is less than about 0.20 dB/km.
Further aspects of the present invention relate to methods of making glasses of the present invention, methods of making the optical components of the present invention, optical components in the form of optical fibers and planar waveguides, and optical fiber bundles or optical fiber ribbons that includes optical fibers of the present invention.
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D.A. Pinnow et al, “Investigation of the Soda Aluminosilicate Glass System For Application To Fiber Optical Waveguides”,Mat. Res. Bull., vol. 10 (1975). pp. 133-146.
K. Shiraki et al. “Optical properties of sodium alminosilicate glass”,Journal of Non-Crystalline Solids, 149 (1992). pp. 243-248.
P.I. Higby et al, “Gallogermanate Glasses as Nar IR Optical Waveguides”.Mat. Res. Soc. Symp. Proc., vol. 244 (1992). pp. 115-120.
S. Todoroki et al, “Alkali Magnesium/Zinc Silicate Glasses with Low Rayleigh Scattering”,J. Am. Ceram. Soc. 78(9)(1995), pp. 2566-2568.
A. Berezin. “Total internal reflection on isotopic interface: a case for isotopic fiber optics”. Josa Communications, J. Opt. Soc. Am. B, vol. 5, No. 3. Mar. 1988. pp. 728-729.
Andrus Ronald L.
Logunov Stephan L.
Sen Sabyasachi
Carlson Robert L.
Corning Incorporated
Palmer Phan T. H.
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