A combined OCT/pressure sensor system includes an optical cable comprising a single-mode core and a multi-mode core. An OCT optical imaging sensor near a distal end of the optical cable can be inserted into a lumen of a living being. First light exiting a distal end of the single-mode core illuminates an interior of the lumen. The OCT optical imaging sensor acquires image information about the interior of the lumen and transmits an optical signal carrying the image information into the distal end of the single-mode core, toward a proximal end of the single-mode core. An optical pressure sensor attached near the OCT optical imaging sensor receives second light from the distal end of the optical cable, senses ambient pressure within the lumen and transmits an optical signal indicative of the ambient pressure into a distal end of the multi-mode core, toward a proximal end of the multi-mode core.

A space-division multiplexed optical fiber includes a relatively high refractive index optical core region surrounded by alternating regions of relatively low and relative high refractive index material, forming concentric high index rings around the core. The optical core region supports propagation of light along at least a first radial mode associated with the optical core region and a high index ring region supports propagation of light along at least a second radial mode associated with the high index ring region. The second radial mode is different from the first radial mode.

An optical fiber according to an embodiment has a structure for enabling determination of improvement in transmission loss at a preform stage. The optical fiber includes: a core containing Cl and having an average refractive index lower than a refractive index of pure silica glass; a first cladding containing F; a second cladding; and a resin coating, in which an effective area at a wavelength of 1550 nm is 135 m.sup.2 or more and 170 m.sup.2 or less, a ratio of the effective area to a cutoff wavelength .sub.C is 85.0 m or more, a bending loss of an LP01 mode at a wavelength of 1550 nm and at a bending radius of R15 mm is less than 4.9 dB per 10 turns, and the resin coating includes a primary resin layer having a Young's modulus of 0.3 MPa or less.

In various embodiments, the beam parameter product and/or numerical aperture of a laser beam is adjusted utilizing a step-clad optical fiber having a central core, a first cladding, an annular core, and a second cladding.

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 space-division multiplexed optical fiber includes a relatively high refractive index optical core region surrounded by alternating regions of relatively low and relative high refractive index material, forming concentric high index rings around the core. The optical core region supports propagation of light along at least a first radial mode associated with the optical core region and a high index ring region supports propagation of light along at least a second radial mode associated with the high index ring region. The second radial mode is different from the first radial mode.

An optical fiber includes (i) a chlorine doped silica based core having a core alpha (Core.sub.)4, a radius r.sub.1, and a maximum refractive index delta .sub.1max % and (ii) a cladding surrounding the core. The cladding surrounding the core includes a) a first inner cladding region adjacent to and in contact with the core and having a refractive index delta .sub.2, a radius r.sub.2, and a minimum refractive index delta .sub.2min such that .sub.2min<.sub.1max, b) a second inner cladding adjacent to and in contact with the first inner cladding having a refractive index .sub.3, a radius r.sub.3, and a minimum refractive index delta .sub.3min such that .sub.3min<.sub.2, and c) an outer cladding region surrounding the second inner cladding region and having a refractive index .sub.5, a radius r.sub.max, and a minimum refractive index delta .sub.3min such that .sub.3min<.sub.2. The optical fiber has a mode field diameter MFD at 1310 of 9 microns, a cable cutoff of 1260 nm, a zero dispersion wavelength of 1300 nmzero dispersion wavelength 1324 nm, and a macrobending loss at 1550 nm for a 20 mm mandrel of less than 0.75 dB/turn.

An optical fiber includes (i) a chlorine doped silica based core having a core alpha (Core.sub.)4, a radius r.sub.1, and a maximum refractive index delta .sub.1 max% and (ii) a cladding surrounding the core. The cladding surrounding the core includes a) a first inner cladding region adjacent to and in contact with the core and having a refractive index delta .sub.2, a radius r.sub.2, and a minimum refractive index delta .sub.2 min such that .sub.2 min<.sub.1 max, b) a second inner cladding adjacent to and in contact with the first inner cladding having a refractive index .sub.3, a radius r.sub.3, and a minimum refractive index delta .sub.3 min such that .sub.3 min<.sub.2, and c) an outer cladding region surrounding the second inner cladding region and having a refractive index .sub.5, a radius r.sub.max, and a minimum refractive index delta .sub.3 min such that .sub.3 min<.sub.2. The optical fiber has a mode field diameter MFD at 1310 of 9 microns, a cable cutoff of 1260 nm, a zero dispersion wavelength of 1300 nmzero dispersion wavelength 1324 nm, and a macrobending loss at 1550 nm for a 20 mm mandrel of less than 0.75 dB/turn.

An illumination system for a surgical device is provided. The illumination system includes a tubular body made of a light permeable material and having at least one lumen extending between a distal end and a proximal end. The illumination system further includes a light source. At least one light diffusing optical fiber is disposed in the at least one lumen, the at least one light diffusing optical fiber having a core, primary cladding, and a plurality of nano-sized structures, the optical fiber further including an outer surface, and an end optically coupled to the light source. The fiber is configured to scatter guided light via the nano-sized structures away from the core and through the outer surface, to form a light-source fiber portion having a length that emits substantially uniform radiation over its length.

An optical fiber includes: a core; a cladding layer that is lower in refractive index than the core; and a depressed layer that lies between the core and the cladding layer and that is lower in refractive index than the cladding layer, wherein: the optical fiber has an effective core area Aeff that is equal to or greater than 100 m.sup.2 and equal to or less than 129 m.sup.2, the core has a radius r1 that is equal to or greater than 5.2 m and equal to or less than 7.4 m, the core has a refractive index volume Vcore that is equal to or greater than 8.5% m.sup.2 and equal to or less than 16.5% m.sup.2, the depressed layer has a refractive index volume Vdep that is equal to or greater than 40% m.sup.2 and less than 0% m.sup.2.