Fiber-based mid-IR signal combiner and method of making same

A mid-infrared (mid-IR) signal transmitting device, comprising:

• a plurality of mid-IR transmitting optical input fibers each constructed to transmit a mode of a corresponding optical signal, wherein each of the plurality of optical input fibers includes:
• an input core and an input cladding having a first refractive index;
• a mid-IR transmitting glass tube having a second refractive index lower than the first refractive index of the input claddings of the plurality of optical input fibers;
• and
• a jacketing disposed around a periphery of the mid-1R transmitting glass tube,
• wherein in a first region of the device the plurality of optical input fibers are not disposed within the glass tube,
• wherein in a second region of the device, disposed downstream of the first region in a direction of optical signal propagation, the plurality of optical input fibers are disposed within the glass tube, and for each of the optical input fibers a diameter of the input core is sufficient to confine the mode of the optical signal to the input core, and
• wherein in a third region of the device, disposed downstream of the second region in the direction of optical signal propagation, the plurality of optical input fibers, the glass tube, and the jacketing are tapered such that their respective outer diameters decrease in magnitude in the direction of signal propagation, and in a portion of the third region, outer diameters of the input cores of the plurality of optical input fibers are insufficient to confine the modes of the respective optical signals to the input cores and the optical signals are dejected from the input cores to propagate through an output core formed from the input claddings of the plurality of optical input fibers, and
• wherein in a fourth region of the device, disposed adjacent to and downstream of the third region in the direction of signal propagation and extending to an end of the mid-IR signal transmitting device, the outer diameter of the jacketing is substantially the same and less than the outer diameter of the jacketing in the third region.