A polarization maintaining fiber includes: a core; an inner cladding enclosing the core; two stress applying parts that sandwich the inner cladding therebetween; and an outer cladding enclosing the inner cladding and the two stress applying parts. Each of the two stress applying parts is depressed inward against the inner cladding, and the core has a flattened cross section having a long-axis that corresponds to a direction in which the two stress applying parts are aligned.

The present application provides a process of fabrication of erbium and ytterbium-co-doped multielements silica glass based cladding-pumped fiber for use as a highly efficient high power optical amplifier.

A method for forming an optical fiber preform is provided. The method includes inserting a glass core cane into a glass sleeve such that the glass sleeve surrounds a portion of the glass core cane and such that there is a gap between the glass sleeve and the portion of the glass core cane surrounded by the glass sleeve. The method further includes depositing silica soot onto at least a portion of the glass core cane and at least a portion of the glass sleeve to form a silica soot preform, and flowing gas through the gap during processing of the silica soot preform.

The present embodiment relates to a production method for matching a shape of a refractive index profile of a core preform with an ideal curve with high precision and in a short time. Prior to a glass synthesis step of stacking a plurality of glass layers including a refractive index adjusting agent of a predetermined amount on an inner peripheral surface or on an outer peripheral surface of a glass deposition substrate, glass synthesis actual-result data is created from production condition data of a glass preform produced in the past and refractive index profile data of a core preform obtained from the glass preform. In each glass synthesis section where the glass synthesis step is executed, a doping amount of the refractive index adjusting agent is adjusted on the basis of the glass synthesis actual-result data.

A radiation-resistant laser optical fiber preform core rod at least includes one type of activated ion (Yb.sup.3+, Er.sup.3+) and one or more types of co-doped ion (Al.sup.3+, P.sup.5+, Ge.sup.4+, Ce.sup.3+, F.sup.?), and OD group of 16-118 ppm. Irradiation resistance of core rod glass can be effectively improved by sequentially performing pre-treatments, i.e. deuterium loading, pre-irradiation and thermal annealing on a preform core rod. Electron paramagnetic resonance test shows that, under the same radiation condition, the radiation induced color center concentration in a preform core rod treated by the method above is lower than in an untreated core rod by one or more orders of magnitude. The obtained core rod can be used for preparing a radiation-resistant rare earth-doped silica fiber, and has the advantages of high laser slope efficiency, low background loss, being able to be used stably in a vacuum environment for a long time, for example.

An optical fiber package is described comprising a light transmitting core having a core diameter, a coating layer surrounding the core, and wherein the amount of chlorine in the light transmitting core region is homogeneous and comprises at least 3000 ppm. The fiber package is such that the optical fiber core exhibits a reduction in the hydrogen induced attenuation losses. A method for fabricating the optical fiber package is also disclosed.

An optical fiber has a core region that is doped with one or more viscosity-reducing dopants in respective amounts that are configured, such that, in a Raman spectrum with a frequency shift of approximately 600 cm.sup.1, the fiber has a nanoscale structure having an integrated D2 line defect intensity of less than 0.025. Alternatively, the core region is doped with one or more viscosity-reducing dopants in respective amounts that are configured such that the fiber has a residual axial compressive stress with a stress magnitude of more than 20 MPa and a stress radial extent between 2 and 7 times the core radius. According to another aspect of the invention a majority of the optical propagation through the fiber is supported by an identified group of fiber regions comprising the core region and one or more adjacent cladding regions. The fiber regions are doped with one or more viscosity-reducing dopants in respective amounts and radial positions that are configured to achieve viscosity matching among the fiber regions in the identified group.

According to embodiments, an optical fiber may include a core portion comprising an outer radius r.sub.C and a maximum relative refractive index .sub.Cmax. A cladding may surround the core portion and include a low-index trench and an outer cladding. The low index trench may surround the core portion and includes an outer radius r.sub.T and relative refractive index .sub.T. The outer cladding may surround and be in direct contact with the low-index trench. The outer cladding may be formed from silica-based glass comprising greater than 1.0 wt. % bromine and has a relative refractive index .sub.OC, wherein .sub.Cmax>.sub.OC>.sub.T. The optical fiber may have a cable cutoff of less than or equal to 1530 nm. An attenuation of the optical fiber may be less than or equal to 0.185 dB/km at a wavelength of 1550 nm.

A method for preparing a doped optical fibre preform includes formulating, a rare earth material or a functional metal material and a co-doping agent into a doping solution, mixing a high-purity quartz powder with the doping solution, drying same at a temperature of 100C.-150C. for 12-48 hours, crushing and screening the same to obtain a doped quartz powder; depositing the doped quartz powder onto the surface of a target rod to form a doped core layer; replacing the doped quartz powder with the high-purity quartz powder, and depositing the high-purity quartz powder onto the surface of the doped core layer to form a quartz outer cladding; and removing the target rod, and gradually collapsing the entirety formed from the doped core layer and the quartz outer cladding at a high temperature to obtain the doped optical fibre preform.

The present invention provides a large-effective-mode-area low-loss optical fiber with optimized cladding components, which comprises a core layer and a cladding comprising, from the inside to the outside, a first sinking layer, a second sinking layer, an optional third sinking layer, and an outer cladding. In the present invention, phosphorus and aluminum are co-doped in the optical fiber cladding, to form a tetrahedron [AlPO.sub.4] in glass, thus optimizing the viscosity of the cladding while effectively reducing the refractive index of the cladding, without causing increased hydrogen loss. The process is simple, and highly repeatable.