Optical waveguides – With disengagable mechanical connector – Structure surrounding optical fiber-to-fiber connection
Reexamination Certificate
2002-08-30
2004-09-28
Lee, John D. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Structure surrounding optical fiber-to-fiber connection
C385S017000
Reexamination Certificate
active
06796718
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a micro linear positioner, particularly developed for optical switches, and a manufacturing method for such micro linear positioners and/or optical switches. An electromagnetic coil moving a magnet between two latched positions in the device controls the switch-path of the positioner.
DESCRIPTION OF RELATED ART
Many modern optical systems use light beams, usually laser-generated, to carry various types of information. Within the optical system, a light beam may alternate between travelling in free space and/or travelling in a fibre or another optical conductor. Amongst many other applications, the technology can be used for example to combine computers with mechanical devices such as sensors, valves, gears, mirrors, and actuators, etc. Many optical systems, such as fibre-optic micromechanical devices, e.g. in telecommunication systems etc. utilizing optical fibres, require the use of optical switches for selectively coupling signal sources to one or more destinations. In the field of micro-technology, micro-electromechanical systems (MEMS) switches formed on single-crystal silicon wafer substrata are used for the coupling of the signals. These optical switches are normally actuated by thermal, piezoelectric, or electrostatic means embedded in the silicon wafer substrate. However, many fibre-optic micromechanical devices do not fit that small order of magnitude, and micromechanical optical switches of larger dimensions are needed where thermal or piezoelectric actuators no longer can be used. Therefore in the field of fibre-optic communications, there is a need for electromechanical micro-actuated optical switches. The function of the switch is to direct/redirect laser beams from one channel to another within a maximum time of 10 ms. These switches are typically electromechanical and operate by moving a mirror or filter to either permit or deviate passage of a laser beam through a gate. The switch toggles between two latched positions to operate as a binary switch. By placing the switches in a matrix or an array coupled by fibre-optic collimators rendering divergent or convergent rays more nearly parallel, it is possible to control the passage of information through the matrix. In planar optical components, such a matrix can be realized by positioning the switches, each having a mirror or filter in a diagonal slot formed in the intersection of crossing light paths having ports facing the slot. The mirror is moved laterally to reflect incoming light from one fibre to an adjacent fibre communicating with the slot to perform a switching function. Such devices for e.g. a 4×4 input/output switch module require a matrix of 16 switches, i.e. the number of required switches goes with the square of the input and output slots, if the matrix is symmetric in input and output slots. In the case of a 4×1 or 2×1 input/output switch module, the number of required switches is input x output
As mentioned, in optical systems, a light beam may alternate between travelling in free space and travelling in a fibre. This free-space-to-fibre coupling often occurs in the context of an optical switch. It is important for a switch that the free-space-to-fibre coupling be efficient to avoid unnecessary losses of light. Coupling efficiency is especially important in optical systems where light beams are sent through one collimated fibre to another collimated fibre. If the free-space-to-fibre coupling is not efficient then the amount of light coupled through the fibre might be insufficient for the intended purpose. Therefore to maximise the amount of light coupled to the fibre, it is desirable to make the switch as small as possible due to the limited distance through which a laser beam can travel in free space between two collimators. In addition a smaller switch design permits configuring more switch devices to form a single matrix or array of switches. Switch matrices can in turn also handle more switches, thereby permitting the design of more sophisticated gates.
However, current micro positioner design places limits on switch size reductions. Current micro positioners that produce a linear movement typically have a casing size of 11 mm in length with a 2 mm stroke. Permanent magnets are commonly arranged at opposite ends of the coils to hold a moving element in place (latched position) when the device is not energized. This requires space to prevent interference between the two different magnetic fields created by the two permanent magnets. This need for separation effectively places a lower size limit on micro positioners with two permanent magnets. Moreover, since the number of required switches in the matrix goes by the square of the input and output slots, respectively, the size of the switches can be an important feature for the realization of a planar optical component (e.g. a 16×16 input/output switch module requires already 256 switches). Therefore, although prior devices based on current micro positioners provide switching functions, they are difficult to manufacture and limited in the reduction of their size which causes the aforementioned problems. Furthermore, current micro positioners may be subject to temperature and environmental fluctuations, particularly because they employ materials that can expand and contract due to temperature fluctuations.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a smaller micro positioner which does not exhibit the above-described drawbacks. In particular, it should be possible for the positioner to maintain performance and reliability despite being of smaller size. It is a further object of the present invention to permit the micro positioner to be scaled down properly, maximise the efficiency of transmitting light through an optical component with a matrix of switches, reduce switching time to a maximum of 5 ms, and, as a final object, to also enhance reliability by the selection of low friction and low thermal expansive materials.
According to the present invention, this object is achieved particularly though the elements of the independent claim. Moreover, further advantageous embodiments follow from the dependent claims and the specification.
The objects of the invention are also achieved in particular in that an electromagnetic positioner or actuator comprises a piston, which piston is movable between a first and a second predefined position and which piston is held by a piston guide, the movable piston comprising a permanent magnet directed perpendicular to the direction of movement the piston comprising an electromagnetic coil, capable of polarity reversal, in the direction of movement of the piston, by means of which coil, in accordance with its magnetisation, the piston is movable from the one predefined position into the other predefined position, and the coil core, capable of polarity reversal, possesses a magnetic remanence by means of which the movable piston is fixable in one of the two predefined positions when the coil is switched off, i.e. not energized. The piston can be of cylindrical design with a cylindrical piston guide. It can also have a different shape such as, e.g. rectangular. The permanent magnet can be disposed on the piston at the end, for example, it also being conceivable for it to be integrated in the piston at a different place. It can be advantageous, if said permanent magnet and/or said electromagnetic coil are axially magnetized in the direction of motion of said piston. This has inter alia the advantage that the application of force by means of the magnet can be maximized. The permanent magnet of the piston can have e.g. an inductance (B) of 1.2-1.6 T and a coercive field of 940 000-1 000 000 A/m. This has the advantage that, with the typical dimensions for a micro linear positioner, it can correspond to the required signal strength. The magnet core, capable of polarity reversal, can consist e.g. at least partially of a semi-hard magnetic material. The piston and the magnet coil with magnetic core can be separa
Hug Kurt
Jones Peter
Maag Urs
Lee John D.
Lin Tina M
Microcut AG
Oliff & Berridg,e PLC
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