A few mode optical fiber that includes an optical core and an optical cladding surrounding the optical core. The FMF has a step-index profile. The optical core has a core outer radius R.sub.17.5 m and a core refractive index difference n.sub.1 such that 14.510.sup.3<n.sub.1<2410.sup.3. The optical cladding comprises: an index ring with: a ring inner radius R.sub.r1 between 12 m and 19 m; a ring refractive index difference n.sub.r such that n.sub.1/n.sub.r is between 2 and 4; a ring volume V.sub.ring=n.sub.r(Rr.sub.2.sup.2Rr.sub.1.sup.2) between 1.8 m.sup.2 and 4.1 m.sup.2 where R.sub.r2 is the ring outer radius; an inner cladding between the optical core and the index ring, with an inner cladding inner radius R.sub.i1 and an inner cladding outer radius R.sub.i2, the inner cladding having an inner cladding refractive index difference n.sub.clad1 between 1.010.sup.3 and 1.010.sup.3.

A specialized, dispersion-controlled fiber is particularly configured to exhibit a relatively uniform dispersion (D) over a broad spectral range (for example, 1000 nm to 2000 nm). The specialized fiber exhibits an essentially constant attenuation () over this same spectral range so that the fiber is defined as having a high figure of merit (FoM) where FoM is defined as |D|/. The specialized fiber is well-suited for use as a pulse stretcher, providing the ability to separate out wavelength constituents of an extremely short (fs, ps) broadband pulse into the ns range, for example.

A few mode optical fiber that includes an optical core and an optical cladding surrounding the optical core. The FMF has a step-index profile. The optical core has a core outer radius R.sub.17.5 m and a core refractive index difference n.sub.1 such that 14.510.sup.3<n.sub.1<2410.sup.3. The optical cladding comprises: an index ring with: a ring inner radius R.sub.r1 between 12 m and 19 m; a ring refractive index difference n.sub.r such that n.sub.1/n.sub.r is between 2 and 4; a ring volume V.sub.ring=n.sub.r(Rr.sub.2.sup.2Rr.sub.1.sup.2) between 1.8 m.sup.2 and 4.1 m.sup.2 where R.sub.r2 is the ring outer radius; an inner cladding between the optical core and the index ring, with an inner cladding inner radius R.sub.i1 and an inner cladding outer radius R.sub.i2, the inner cladding having an inner cladding refractive index difference .sub.clad1 between 1.010.sup.3 and 1.010.sup.3.

A method of tailoring beam characteristics of a laser beam during fabrication of an electronic device. The method includes: providing a substrate comprising one or more layers; adjusting one or more characteristics of a laser beam; and impinging the laser beam having the adjusted beam characteristics on the substrate to carry out at least one process step for fabricating the electronic device. The adjusting of the laser beam comprises: perturbing the laser beam propagating within a first length of fiber to adjust the one or more beam characteristics of the laser beam in the first length of fiber or a second length of fiber or a combination thereof, the second length of fiber having two or more confinement regions; coupling the perturbed laser beam into the second length of fiber; and emitting the laser beam having the adjusted beam characteristics from the second length of fiber.

A specialized, dispersion-controlled fiber is particularly configured to exhibit a relatively uniform dispersion (D) over a broad spectral range (for example, 1000 nm to 2000 nm). The specialized fiber exhibits an essentially constant attenuation () over this same spectral range so that the fiber is defined as having a high figure of merit (FoM) where FoM is defined as |D|/. The specialized fiber is well-suited for use as a pulse stretcher, providing the ability to separate out wavelength constituents of an extremely short (fs, ps) broadband pulse into the ns range, for example.

A specialized, dispersion-controlled fiber is particularly configured to exhibit a relatively uniform dispersion (D) over a broad spectral range (for example, 1000 nm to 2000 nm). The specialized fiber exhibits an essentially constant attenuation () over this same spectral range so that the fiber is defined as having a high figure of merit (FoM) where FoM is defined as |D|/. The specialized fiber is well-suited for use as a pulse stretcher, providing the ability to separate out wavelength constituents of an extremely short (fs, ps) broadband pulse into the ns range, for example.

Provided is an optical fiber containing an alkali metal element or the like having a smaller diffusion coefficient than K and having a low Rayleigh scattering loss. An optical fiber is composed of silica glass and includes a core and a cladding arranged to surround the core which has a lower refractive index than the core. The core includes a first core including a central axis and a second core arranged to surround the first core. The average concentration of an alkali metal element or alkaline-earth metal element in the first core is 10 mol ppm or less. The average concentration of chlorine in the first core is 2000 mol ppm or more. The average concentration of an alkali metal element or alkaline-earth metal element in the second core is 10 mol ppm or more. The average concentration of chlorine in the second core is 10 to 600 mol ppm.

To mitigate the accuracy of misalignment to reduce costs, and to suppress an inter-mode propagation delay difference to enable high-quality transmission of signals. An optical waveguide is configured to propagate only a fundamental mode at a first wavelength and propagate at least a first-order mode as well as the fundamental mode at a second wavelength. The optical waveguide is configured such that a refractive index distribution of a core and a cladding is controlled so that the inter-mode propagation delay difference is within a predetermined threshold, for example, the inter-mode propagation delay difference is zero, when communication is performed using light of the second wavelength. For example, the first wavelength is in a 1310-nm band and the second wavelength is in an 850-nm band.

The refractive index of a fiber core of a few mode optical fiber is n1. A cladding layer surrounding the fiber core includes: a downward-concave cladding layer surrounding the fiber core, the refractive index thereof is n2; a first upward-convex cladding layer surrounding the downward-concave cladding layer, the refractive index thereof is n3; a second upward-convex cladding layer surrounding the first upward-convex cladding layer, the refractive index thereof is n4; an outer layer surrounding the second upward-convex cladding layer, the refractive index thereof is n5. The refractive indexes of the fiber core, the downward-concave cladding layer, the first upward-convex cladding layer, the second upward-convex cladding layer, the outer layer satisfy: n.sub.1>n3>n.sub.4>n.sub.5>n.sub.2. The fiber is a non-single mode in a direct waveguide state, and equivalent single-mode transmission can be achieved when the optical fiber is bent at a specific bending radius.

An optical fiber with ultra-low attenuation and large effective-area includes a core layer and cladding layers. The cladding layers have an inner cladding layer surrounding the core layer, a trench cladding layer surrounding the inner cladding layer, an auxiliary outer cladding layer surrounding the trench cladding layer, and an outer cladding layer surrounding the auxiliary outer cladding layer. The core layer has a radius of 4.8-6.5 m, and a relative refractive index difference of 0.06% to 0.10%. The inner cladding layer has a radius of 9-15 m, and a relative refractive index difference of about 0.40% to 0.15%. The trench cladding layer has a radius of about 12-17 m, and a relative refractive index difference of about 0.8% to 0.3%. The auxiliary outer cladding layer has a radius of about 37-50 m, and a relative refractive index difference of about 0.6% to 0.25%. The outer cladding layer is a pure silicon-dioxide glass layer.