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A optical switch or relay is described by which a terminal station can be either inserted into a fiber ring or bypassed by closing the fiber ring. The switch has no moving mechanical parts.
English (United States)
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Bypass Switch for Optical Fiber Ring Network
A optical switch or relay is described by which a terminal station can be
either inserted into a fiber ring or bypassed by closing the fiber ring. The switch
has no moving mechanical parts.
Fig. 1 shows the principle. An optical fiber ring has incoming and outgoing
branches A and D, and a terminal station 1 is connected between fiber branches
B and D. All four fiber branches are coupled to the optical bypass switch 2.
It consists of two quarter-pitch GRIN (graded refractive index) rod lenses
which are aligned with respect to their optical axes, and separated by a small gap
of about 0.1-1 mm width. A quarter-pitch GRIN lens has the property that light
emanating from a point source, e.g., a fiber, at the input face of the lens is
expanded to a parallel beam at the other face. With a second GRIN lens, the
parallel beam is refocused at the output face. The four fiber branches A, B, C,
and D are connected symmetrically to the input/output lens faces, as shown.
A transparent channel element 5, comprising different fluids, is arranged that
the gap between the GRIN lenses is always filled by a fluid. The fluids in the
channel element are a transparent fluid 6 matching the optical index of the
lenses, mercury 7, and a ferrofluid 8 which can be shifted between two positions
by two electromagnets M1 and M2.
When magnet M1 is energized, the ferrofluid is in the position shown in Fig.
1, and the gap is filled by mercury. As a result, light from fiber branch A is
reflected at the GRIN rod lens/mercury interface and refocused on fiber B, and
light from fiber C is also reflected and is refocused on fiber D. Thus, terminal 1 is
inserted in the ring.
When magnet M2 is energized, the ferrofluid moves to the right, and mercury
7 leaves the gap which is filled instead by index-matching fluid 6....