Radiation pumped heater/heating element

Abstract

A radiation pumped heater includes a ceramic substrate which is heated by a laser beam to a steady state temperature. An optical fiber is heated by conduction and radiation emitted from the ceramic substrate.

Claims

1. A method for processing an optical fiber comprising: heating a portion of an optical fiber with a radiation pumped heater, the heater comprising a ceramic substrate which is heated by a laser beam to a steady state temperature, and wherein said optical fiber is heated by conduction and radiation emitted from the ceramic substrate; drawing the optical fiber to reduce a diameter of the heated portion; holding said optical fiber with a proximal holder and a distal holder located on opposite sides of the heated portion, and moving said proximal and distal holders to draw the heated portion of said fiber to the reduced diameter, and wherein said proximal holder is moved at a different velocity than said distal holder at some stage in the method.

2. The method according to claim 1, wherein after heating the optical fiber to a temperature that permits drawing the fiber to a reduced diameter, said proximal and distal holders are initially moved in the same direction at the same velocity, and afterwards, said proximal holder is slowed and said distal holder moves faster than said proximal holder.

3. The method according to claim 1, wherein said holders move in the same direction.

4. The method according to claim 1, wherein said holders move in different directions.

5. The method according to claim 1, wherein said ceramic substrate is heated by another laser beam on a side of said optical fiber opposite to said first-mentioned laser beam.

6. The method according to claim 5, wherein said laser beams are symmetrically located on opposite sides of said optical fiber.

7. The method according to claim 1, wherein said laser beam is emitted via a safety shutter and a half-wavelength plate to a variable zoom telescope, and said laser beam passes from said telescope to a cylindrical lens and is then reflected by a mirror to a work area of said optical fiber.

8. A method for processing an optical fiber comprising: heating a portion of an optical fiber with a radiation pumped heater, the heater comprising a ceramic substrate, and wherein said optical fiber is heated by conduction and radiation emitted from the ceramic substrate; and drawing the optical fiber to reduce a diameter of the heated portion; wherein said ceramic substrate is heated by a pair of laser beams on opposite sides of said optical fiber to a steady state temperature.

9. The method according to claim 8, wherein said laser beams are symmetrically located on opposite sides of said optical fiber.

10. The method according to claim 8, wherein for each of said laser beams, said laser beam is emitted via a safety shutter and a half-wavelength plate to a variable zoom telescope, and said laser beam passes from said telescope to a cylindrical lens and is then reflected by a mirror to a work area of said optical fiber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:

(2) FIG. 1 is a simplified illustration of a radiation pumped heater, in accordance with a non-limiting embodiment of the invention, wherein an optical fiber is heated by conduction and radiation emitted from a ceramic substrate illuminated and heated by a laser beam.

(3) FIG. 2 is a simplified illustration of a furnace with a radiation pumped heater, in accordance with a non-limiting embodiment of the invention;

(4) FIG. 3 is a simplified illustration of a radiation pumped heater that includes a ceramic substrate with a depression in which the fiber is placed, in accordance with a non-limiting embodiment of the invention;

(5) FIG. 4 is a simplified illustration of processing the optical fiber with the radiation pumped heater, in accordance with a non-limiting embodiment of the invention;

(6) FIGS. 5A-5C are simplified illustrations of processing the optical fiber with the radiation pumped heater, in accordance with another non-limiting embodiment of the invention; and

(7) FIG. 6 is a simplified illustration of apparatus for processing optical fibers, in accordance with a non-limiting embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(8) Reference is now made to FIG. 1, which illustrates a radiation pumped heater, in accordance with a non-limiting embodiment of the invention, used for optical fiber processing. A ceramic substrate 10, such as a zirconia ceramic, is illuminated by a laser beam 12, such as a CO.sub.2 laser beam. The laser beam 12 is strongly absorbed near the zirconia upper face which in turn rapidly heats until reaching a steady state. When appropriate conditions are established, a few watt CO.sub.2 laser having a beam diameter of the order of one mm, can easily raise the laser-zirconia interaction zone to temperatures acceding 2000° C. in an atmospheric environment. An optical fiber 14 is heated by conduction and radiation emitted from the ceramic substrate 10. The ceramic substrate can maintain this high temperature for an hour or more.

(9) It is noted that the ceramic substrate 10 may be quite porous, and the volume of the pores may constitute 90% or more of the total volume. Such porosity lowers the thermal conductivity (the pores are basically air pockets and air has very poor thermal conductivity). The high porosity also affects the thermal shock resistance of the ceramic substrate 10. It has been found that the zirconia substrate behaved well in tests even when heated rapidly,

(10) Another application for such heating techniques is a miniature-sized furnace, as is now described with reference to FIG. 2. In this embodiment, a ceramic substrate 16 is formed with an internal cavity 18, thus forming a ceramic furnace. The laser beam 12 impinges upon the cavity 18 and heats up the ceramic furnace. The furnace may be used for heating optical fiber 14 in the treatment and production of fiber optic devices, such as but not limited to, tapers, couplers and combiners.

(11) Reference is now made to FIG. 3, which illustrates a radiation pumped heater 25 that includes a ceramic substrate 20 with a depression 22 in which the fiber 14 is placed. The substrate 20 is heated by a pair of laser beams 12 symmetrically on opposite sides of the fiber 14. Thus, in FIG. 1, the laser beam impinges on the optical fiber, whereas in FIG. 3, the beams do not impinge on the fiber.

(12) Reference is now made to FIG. 4, which illustrates processing the optical fiber 14 with the radiation pumped heater 25, in accordance with a non-limiting embodiment of the invention. Two opposite ends of the fiber 14 are held by holding elements 30, such as clamps. The middle portion of the fiber is heated by the heater 25 of FIG. 3. After heating the fiber to a temperature that permits drawing the fiber to a reduced diameter, the holding elements 30 are moved in opposite directions; this causes the middle portion of the fiber to be drawn thinner to a reduced diameter. The process can be carefully and precisely controlled to achieve precise diameters. Heating over the reduced diameter portion should be done uniformly.

(13) Reference is now made to FIGS. 5A-5C, which illustrate processing the optical fiber 14 with the radiation pumped heater 25, in accordance with another non-limiting embodiment of the invention. Here again, two opposite ends of the fiber 14 are held by holding elements 30 and the middle portion of the fiber is heated by heater 25. After heating the fiber to a temperature that permits drawing the fiber to a reduced diameter, the holding elements 30 are initially moved in the same direction at the same velocity (FIG. 5A). Afterwards, the proximal holder 30 (that feeds the fiber to heater 25) is slowed so that the distal holder 30 moves faster (FIG. 5B). This causes the middle portion of the fiber to be drawn thinner to a reduced diameter. Afterwards, the velocity of the proximal holder 30 can be modified, for example, to match that of the distal holder 30 so that the holders move at the same velocity (FIG. 5C); or alternatively moved at different speeds. The diameter and length of the fiber portion with the reduced diameter process can be carefully and precisely controlled, depending on the relative velocities of the holders, temperature and fiber properties, among other factors. Typically, but not necessarily, the method of FIG. 4 (holding elements 30 are moved in opposite directions) is applicable for thicker fibers than the method of FIG. 5.

(14) Reference is now made to FIG. 6, which illustrates apparatus 60 for processing optical fibers, in accordance with a non-limiting embodiment of the invention.

(15) Apparatus 60 includes holders 65 and 66 for holding an optical fiber 14. Motors or actuators 63 and 64 control and establish the relative position of holders 65 and 66, respectively. Motors 63 and 64 and holders 65 and 66 are all mounted on a moving table for movement in the x- and z-axes. The moving table may include a base which is moved by a motor or actuator 61 along the x-axis and another base which is moved by a motor or actuator 62 along the z-axis.

(16) The central portion of the fiber is heated by a radiation pumped heater 67. Camera(s) 68 provide visual monitoring and measurement of the heating and drawing process. A laser 76 (e.g., CO.sub.2 laser) emits a laser beam via a safety shutter 75 and half-wavelength plate 75A (for controlling the beam polarity) to a variable zoom telescope 70. The beam passes from the telescope 70 to a cylindrical lens 71, and is then reflected by a mirror 74 to the work area of the fiber. A beam splitting polarizer 72 splits the beam and one of the beams is directed by another mirror 73 to the work area. Both beams that are directed to the work area may pass through a spherical mirror 69. The beams are directed on the ceramic substrate of heater 67 on opposite sides of the fiber 14 (or on the fiber), as described above.

(17) The telescope 70 is used to control the spot size of the beam on the ceramic and/or fiber. A controller 79 may be provided for controlling the various elements of the apparatus for controlling the process to desired parameters.

(18) The invention has been described above for use with reducing the diameter of an optical fiber. The invention may also be used for thinning and melting more than one fiber and fibers that have different mechanical and/or optical properties. For example, the invention may also be used for producing optical couplers and other optical devices, and for thinning tubes and other structures.