All-Fiber Inline Optical Taps Adopting A Configuration Of Side-Pump Signal-And-Pump Combiners

An all-fiber inline optical tap, comprising:

• a length of double-clad fiber comprising a first core, a first cladding, and a second cladding over the first cladding, the length of double-clad fiber configured to transport an optical signal in the first core with the optical signal bounded in a first interface between the first core and the first cladding, wherein the length of double-clad fiber further comprises a cladding-stripped portion with the second cladding stripped, wherein a part of the cladding-stripped portion comprises a coupling portion, and wherein a combined optical energy propagates in the length of double-clad fiber and is bounded in a second interface between the first cladding and the air around the cladding-stripped portion;
• and
• one or more multimode fibers each respectively comprising a second core, a third cladding, outer claddings and buffer coatings over the third cladding, and a stripped portion with the outer claddings and buffer coatings stripped, wherein a part of the stripped portion comprises a taper portion with a predetermined taper slope with respect to an optical axis of each of the one or more multimode fibers, wherein a plurality of the taper portions embodied in the one or more multimode fibers are configured to be fused around the coupling portion with the third cladding directly coupled with the first cladding, and wherein each of the one or more multimode fibers is configured to respectively extract either a part of the combined optical energy or a part of the optical signal in the length of double-clad fiber,
• wherein:
• the part of the optical signal extracted comprises a leaking signal light escaped out from the first interface due to fiber bending or mismatch in a signal propagation pathway;
• the part of the combined optical energy extracted comprises either an unabsorbed pump residual or other light scattering due to numerous imperfections in fiber components and splices utilized;
• either the part of the combined optical energy or the part of the optical signal is configured to pass through the taper portion with a decreasing divergence angle against an optical axis of the taper portion for each internal reflection, thereby being extracted from the length of double-clad fiber with a reduced optical loss;
• and
• the optical signal, after propagating through the coupling portion, continues to traverse in the first core and is bound in the first interface, thereby passing through the length of double-clad fiber with a reduced signal loss and a reduced beam quality degradation.