Bromine-doped optical fiber

#This specification pertains to optical fibers. More particularly, this specification pertains to optical fibers doped with bromine. Most particular, this specification pertains to an optical fiber having a high index core doped with bromine.

#Optical fiber performance depends on the ability to control refractive index profiles in low loss media. Most typically, silica glass is used as the basis for optical fiber that is used to transmit light over lengths of greater than a few meters to hundreds of kilometers, as the spectral attenuation in the 1300 to 1500 nm range is low, practically as low as 0.18 dB/km for typical single mode fiber products. Optical loss is determined by the Rayleigh scattering of the silica based medium, the concentration of impurities, and wavelength dependent factors such as UV and IR absorption tails. In most single mode fibers, germanium oxide (GeO2) is used to dope a core region of silica glass, increasing the index by 0.35%. Although GeO2 is a relatively expensive dopant, it comprises only about 8% by weight of the core region of the fiber and only about 0.5 wt % of the total glass portion fiber (core+cladding). Germanium doping is also relatively easy to accomplish during blank laydown and complex refractive index profiles can be made simply by varying the ratio of silica and germanium precursors supplied to the burners in an OVD process. SiCl4 and GeCl4 are common precursors for forming Ge-doped silica glass in the core laydown process. A drawback of using Ge as an index-raising dopant for silica cores is that the presence of Ge increases the Rayleigh scattering of the fiber relative to pure silica fibers. As a result, there is interest in identifying alternate dopants that enable the refractive index profile control needed in optical fibers to achieve fibers at reasonable cost that exhibit lower attenuation losses due to Rayleigh scattering.

#Two approaches for producing ultralow loss fibers have been commercialized. In one approach, a silica core is modified by alkali doping at low concentration (e.g. 0.1 wt % K2O or less). The alkali doping concentration is designed to be (1) high enough to reduce Rayleigh scattering by lowering the viscosity of the glass to a degree sufficient to produce a fiber core with a low fictive temperature and (2) sufficiently low to avoid increases in Rayleigh scattering resulting from compositional inhomogeneities. Since alkali doping at low concentration does not lead to a significant increase in the refractive index of the core relative to undoped silica, the refractive index profile is controlled by doping a surrounding silica cladding with F (fluorine). The presence of fluorine in the silica cladding reduces the refractive index of the cladding relative to undoped silica and provides a mechanism for achieving the core-cladding refractive index contrast needed for effective waveguiding in an optical fiber. The process required to make fibers with alkali-doped cores is complicated and expensive, but attenuation of ˜0.15 dB/km is possible

#While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the written description, it is believed that the specification will be better understood from the following written description when taken in conjunction with the accompanying drawings, wherein:

#FIG. 1 depicts the cross-section of an optical fiber having a core, an inner cladding, an outer cladding, a primary coating, and a secondary coating.

#FIG. 2 depicts a relative refractive index profile for an optical fiber having a core, an inner cladding, and an outer cladding.

#The embodiments set forth in the drawings are illustrative in nature and not intended to be limiting of the scope of the detailed description or claims. Whenever possible, the same reference numeral will be used throughout the drawings to refer to the same or like feature.

#The present disclosure is provided as an enabling teaching and can be understood more readily by reference to the following description, drawings, examples, and claims. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the embodiments described herein, while still obtaining the beneficial results. It will also be apparent that some of the desired benefits of the present embodiments can be obtained by selecting some of the features without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations are possible and can even be desirable in certain circumstances and are a part of the present disclosure. Therefore, it is to be understood that this disclosure is not limited to the specific compositions, articles, devices, and methods disclosed unless otherwise specified. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

#Disclosed are materials, compounds, compositions, and components that can be used for, can be used in conjunction with, can be used in preparation for, or are embodiments of the disclosed method and compositions. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these compounds may not be explicitly disclosed, each is specifically contemplated and described herein. Thus, if a class of substituents A, B, and/or C are disclosed as well as a class of substituents D, E, and/or F, and an example of a combination embodiment, A-D is disclosed, then each is individually and collectively contemplated. Thus, in this example, each of the combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are specifically contemplated and should be considered disclosed from disclosure of A, B, and/or C; D, E, and/or F; and the example combination A-D. Likewise, any subset or combination of these is also specifically contemplated and disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E are specifically contemplated and should be considered disclosed from disclosure of A, B, and/or C; D, E, and/or F; and the example combination A-D. This concept applies to all aspects of this disclosure including, but not limited to any components of the compositions and steps in methods of making and using the disclosed compositions. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific embodiment or combination of embodiments of the disclosed methods, and that each such combination is specifically contemplated and should be considered disclosed.