Even when excitation light having large power is used, damage at the end face of the optical fiber is suppressed, and reduction in wavelength conversion efficiency and reduction in phase sensitive amplification gain are prevented. An embodiment of the present invention relates to a wavelength conversion apparatus for performing a wavelength conversion operation by inputting a fundamental wave and a second-order harmonic into a second-order nonlinear optical medium, the wavelength conversion apparatus comprising: a second-order harmonic input optical fiber optically coupled to a waveguide of the second-order nonlinear optical medium, for inputting the second-order harmonic into the waveguide; and a second-order harmonic output optical fiber optically coupled to a waveguide, for outputting the second-order harmonic output from the waveguide, wherein the second-order harmonic input optical fiber and the second-order harmonic output optical fiber are polarization maintaining fibers.

A method of manufacturing a multimode optical fiber includes specifying a peak wavelength λ.sub.P for the multimode optical fiber. The peak wavelength λ.sub.P corresponds to a wavelength at which the multimode optical fiber has a maximum bandwidth. The multimode optical fiber comprises a core and a cladding surrounding and directly adjacent to the core. The core has a radius r.sub.1 and a maximum relative refractive index Δ.sub.1,MAX>0. The cladding comprises a depressed-index region having a minimum relative refractive index Δ.sub.3,MIN<0 and a volume v. A draw tension T for the multimode optical fiber is selected based on a correlation relating peak wavelength λ.sub.P to draw tension T, the correlation comprising a correlation constant. The correlation constant K is a function of at least one of Δ.sub.1,MAX, r.sub.1, v, Δ.sub.3,MIN, and λ.sub.P. The multimode optical fiber is drawn from a preform at the draw tension T.

A system for outputting partially spatially coherent light to an imaging system is disclosed herein, which includes a spatially coherent light source configured to output a spatially coherent signal, at least one optical device having an optical device body with a first device surface formed thereon and configured to reflect a portion of the spatially coherent signal to form at least one coherent reflected signal. The optical device body also includes a second device surface having one or more surface irregularities configured to diffuse a portion of the spatially coherent light source output signal transmitted through the optical device body, to produce at least one spatially incoherent signal. The combination of the coherent reflected signal and the spatially incoherent signal form the partially spatially coherent light signal.

A multi-core fiber includes: a plurality of core portions each including a central core portion, an intermediate layer formed on an outer periphery of the central core portion, and a trench layer formed on an outer periphery of the intermediate layer; and a cladding portion formed on an outer periphery of the plurality of core portions, wherein in each of the plurality of core portions, Δ1>Δ2>Δ3 and 0%>Δ3>−0.3% are satisfied, where Δ1 is an average maximum relative refractive-index difference of the central core portion, Δ2 is an average relative refractive-index difference of the intermediate layer, and Δ3 is an average relative refractive-index difference of the trench layer, with respect to the cladding portion.

A method for mitigating modal noise includes applying a time-varying mechanical force to a fiber segment of the multimode optical fiber in at least a first direction orthogonal to a fiber axis of the multimode optical fiber within the fiber segment. A modal-noise mitigator for a multimode optical fiber includes an actuator configured to apply a time-varying mechanical force to a fiber segment of the multimode optical fiber in at least a first direction orthogonal to a fiber axis of the multimode optical fiber within the fiber segment.

A method of processing by controlling one or more beam characteristics of an optical beam may include: launching the optical beam into a first length of fiber having a first refractive-index profile (RIP); coupling the optical beam from the first length of fiber into a second length of fiber having a second RIP and one or more confinement regions; modifying the one or more beam characteristics of the optical beam in the first length of fiber, in the second length of fiber, or in the first and second lengths of fiber; confining the modified one or more beam characteristics of the optical beam within the one or more confinement regions of the second length of fiber; and/or generating an output beam, having the modified one or more beam characteristics of the optical beam, from the second length of fiber. The first RIP may differ from the second RIP.

A first multimode optical fiber carries a mode division multiplexed (MDM) optical signal. The MDM optical signal is transmitted into a second multimode fiber from the first multimode optical fiber. The first and second multimode fibers are coupled via a fiber connector. The lateral offset between the two fibers at the connector is less than 2 μm.

Example implementations described herein are directed to a system involving one or more photonic integrated circuits having multi-mode waveguides and connected to a printed optical board through the use of multi-mode waveguide connectors described herein. The printed optical board can include an embedded multi-mode waveguide bus to facilitate optical signal to and from the photonic integrated circuits. The system can also include a chiplet such as a photonic integrated circuit with a single mode waveguide configured to connect to an optical fiber cable.

Methods for classifying a core cane of an multimode optical fiber are disclosed. In embodiments, the method includes determining a relative refractive index profile Δ(r) of the core cane; fitting the relative refractive index profile Δ(r) to an alpha profile Δ.sub.fit(r) defined by:

[00001]${\Delta }_{\mathrm{fit}}\left(r\right)={\Delta }_{o,\mathrm{fit}}\left(1-{\left(\frac{r}{a_{\mathrm{fit}}}\right)}^{{\alpha }_{\mathrm{fit}}}\right)$

where Δ.sub.o,fit is a relative refractive index at a longitudinal centerline of the core cane, α.sub.fit is a core shape parameter, and a.sub.fit is an outer radius of the core cane; generating a non-alpha residual profile Δ.sub.diff(r)=Δ(r)−Δ.sub.fit(r) for the core cane; computing one or more metrics from Δ.sub.diff(r), and using the one or metrics in a classification of the core cane, the classification comprising a prediction of whether a bandwidth at a pre-determined wavelength of an optical fiber drawn from a preform comprising the core cane exceeds a pre-determined bandwidth at the pre-determined wavelength.

A laser device includes: a laser unit that outputs laser light; an output end that launches the laser light; a first fusion splice portion; and a second fusion splice portion. In each of the first fusion splice portion and the second fusion splice portion, two multi-mode fibers are fusion-spliced. Each of the two multi-mode fibers include a core through which the laser light propagates and a cladding that surrounds the core. The first fusion splice portion is disposed closer to the laser unit than is the second fusion splice portion. At least a part of the core in the first fusion splice portion contains a dopant that is the same type as a dopant contained in the cladding in the first fusion splice portion for decreasing a refractive index.