Optical connector polishing jig

In a polishing apparatus an optical connector polishing jig holds the MT ferrule provided at the connection end portion of the optical connector, the optical connector polishing jig includes: a cylinder base; a cylinder shaft held on the cylinder base to be capable of moving in the up-down direction; and a set block connected to an end of the cylinder shaft and having a hole into which the MT ferrule is inserted and in which fixing means for adjusting the pressing force and fixing the MT ferrule is inserted, and a surface of the fixing means that comes into contact with the MT ferrule has a protrusion that partially protrudes to apply a pressing force to the MT ferrule such that when the MT ferrule is fixed, an end surface of the MT ferrule is slightly deformed and a center portion of the end surface in a longitudinal direction swells.

TECHNICAL FIELD

The present invention relates to optical connector polishing jigs and particularly to an optical connector polishing jig used in a polishing apparatus for polishing optical connectors having MT ferrules.

BACKGROUND ART

In recent years, in order to support large capacity optical networks, use of multi-fiber optical fiber has spread, including for connections inside servers used at data centers or the like. In such a background, optical connectors for multi-fiber optical fiber have also been gaining attention instead of ones for single-fiber optical fiber.

FIG.1is a diagram illustrating an example of an optical connector for connecting multi-fiber optical fiber. In the optical connector1, multiple optical fibers10covered with jackets are inserted into an MT ferrule11with the optical fibers exposed at their ends. The description in the present specification is based on the assumption that the length direction of the optical fibers inserted into the MT ferrule11is called the longitudinal direction, and the width direction of the MT ferrule11which is orthogonal to the longitudinal direction is called the lateral direction, as illustrated inFIG.1. The MT ferrule11has a brim11aformed wider than the other portions and an opening11bfor inserting glue. The inside of the MT ferrule11is filled with glue for fixing the optical fibers10inserted into the MT ferrule11to the MT ferrule11, which is injected from the glue injection opening11b. The ends of the optical fibers10inserted inside and the injected glue protrude from at the end surface11cof the MT ferrule11. Since the end surface of the MT ferrule11in this state, into which the optical fibers10are inserted and which is filled with glue, is not suitable for optical connection, it is desirable to polish the end surface to improve the precision of the connection.

For apparatuses for polishing the end surface of the MT ferrule in this state, there are known polishing apparatuses. Such polishing apparatuses include a polishing jig that holds the MT ferrule with its end surface facing down and a polishing plate that, for example, rotates under the polishing jig to polish the end surface of the MT ferrule. The polishing plate is driven in the state where the MT ferrule is inserted and fixed to a specified position in the polishing jig, and the end surface of the MT ferrule can be polished. There are several known techniques about how to hold the MT ferrule in the holding tool in such polishing apparatuses.

Patent literature 1 discloses a configuration in which the MT ferrule is held by pressing the MT optical connector against a side wall of a housing slot inner surface in the lateral direction with a pushing block to fix the MT optical connector. The end surface of the pushing block on the side that pushes the MT optical connector is formed flat.

Patent literature 2 discloses a holding apparatus in which a support wall is provided on a side opposite to a seating portion of a ferrule insertion hole, a holding portion is provided at a front portion facing the support wall, and a holding member having a slope having a down grade toward the back is slidably arranged on the seating portion. In this holding apparatus, a rod member arranged on the slope is pressed downward, pushing the holding member forward, and thus the ferrule is fixed.

Patent literature 3 discloses a method of fixing the optical connector in which an optical connector is inserted from above into a hole one side of which in the lateral direction is open, a clamp pad having at its upper end a flange protrusion for pushing the optical connector from above is brought into contact with the optical connector from the lateral direction, and a clamp screw presses the clamp pad obliquely from above to fix the optical connector.

Patent literature 4 discloses a polishing jig in which a base having an insertion hole into which the ferrule of the optical connector is inserted is provided with a fixation piece for fixing the ferrule, and the fixation piece is fixed with a rotation rod. When the rotation rod rotates, the fixation piece moves to a position for fixing the ferrule.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In general, in the case of connecting multi-fiber optical fiber, it is important for connection quality that the positions of the ends of the optical fibers to be connected are uniform. It is because if the positions are not uniform, it causes a problem that only fibers protruding more are brought into contact, and that optical fibers protruding less are not brought into contact sufficiently with each other. Hence it is important to make the ferrule end-surface11cflat in order to make the positions of the ends of the optical fibers uniform.

The above conventional polishing apparatuses have made it possible to obtain a certain degree of flatness for the end surface of the MT ferrule by polishing.

However, although the flatness of the MT ferrule end-surface requires nanometer-level precision to achieve optical connections having favorable optical characteristics (in terms of connection loss and reflection attenuation), it is actually difficult for any of the polishing apparatuses using the above holding tools to finishes the end surface such that the finished end surface has a high flatness with nanometer-level precision.

Hence, there has been a problem that in the case where the flatness of the end surface of the MT ferrule is low, the end surfaces of multiple optical fibers positioned side by side are ununiform, making some optical connections insufficient, and as a result, favorable optical connections cannot be achieved.

The present invention has been made in light of the problem that conventional apparatuses have, and an object of the present invention is to provide an optical connector polishing jig for a polishing apparatus that provides polishing for achieving a high flatness of the MT ferrule end-surface.

Solution to Problem

To solve the above problem, an aspect of the invention according to a first embodiment is an optical connector polishing jig that holds an MT ferrule of a multi-fiber optical fiber connector in a polishing apparatus for polishing an optical connector, characterized in that the optical connector polishing jig includes fixing means for holding the MT ferrule, and a surface of the fixing means that comes into contact with the MT ferrule has a protrusion that partially protrudes to apply a pressing force to the MT ferrule such that when the MT ferrule is fixed, an end surface of the MT ferrule is slightly deformed and a center portion of the end surface in a longitudinal direction swells.

In an aspect of the invention according to a first aspect of the first embodiment, the fixing means includes an opening into which the MT ferrule is inserted, an inner piece fitted in the opening to be adjacent to the MT ferrule, and a screw that presses the inner piece against the MT ferrule for adjusting the pressing force.

In an aspect of the invention according to a second aspect of the first embodiment, a protrusion formed on a surface of the inner piece that comes into contact with the MT ferrule has any of a center round shape in which only a portion along the center portion protrudes to form a round shape, a T-shape in which a surface protrudes to form the shape of a letter T, and a round shape in which a round shape is formed in whole, such that the pressure applied to a portion along the center portion is larger than the pressure applied to the other portions.

In an aspect of the invention according to a third aspect of the first embodiment, the fixing means includes a lever for pressing a brim of the MT ferrule to an adjoining surface of the opening when the inner piece is pressed to fix the MT ferrule.

In an aspect of the invention according to a fourth aspect of the first embodiment, the adjoining surface of the opening with which the brim of the MT ferrule comes into contact is tilted according to a finished tilt angle of the end surface of the MT ferrule.

In an aspect of the invention according to a fifth aspect of the first embodiment, the polishing apparatus polishes the optical connector by a polishing table horizontally moving relative to the end surface of the MT ferrule, the optical connector polishing jig further includes a housing and a shaft held by the housing such that the shaft is capable of reciprocating and having one end connected to the fixing means, the housing has a cavity receiving the shaft and a spring that expands and contracts along the shaft, and the shaft reciprocates such that in a case where a force that the MT ferrule fixed to the fixing means receives from the polishing table becomes greater than or equal to a certain force, the spring contracts and the shaft moves in a direction toward the housing, and in a case where the force that the MT ferrule fixed to the fixing means receives from the polishing table becomes smaller than the certain force, the spring expands and the shaft moves in a direction away from the housing to a fixed position.

In an aspect of the invention according to a sixth aspect of the first embodiment, the optical connector polishing jig further includes an anti-rotation shaft that is provided on the fixing means to be adjacent to the shaft and to extend in the same direction as the shaft extends and is fitted into the housing.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described in detail.

FIG.2is a perspective view of the outer appearance of a polishing apparatus on which a polishing jig according to the present embodiment is mounted. The polishing apparatus according to the present embodiment is used for polishing the connection end surface11cof a ferrule (MT ferrule, which is hereinafter simply referred to as a ferrule)11housed in an optical connector1as illustrated inFIG.1. This polishing apparatus includes a base101, a polishing table20having a polishing surface for polishing the connection end surface11cof the ferrule11, a support mechanism110that supports the polishing table20, a driving mechanism120that moves the polishing table20in a circular motion and in a reciprocating linear motion, a polishing jig200which is a work holder for holding multiple optical connectors1, and support bases130for supporting the polishing jig200. Here, the circular motion means moving the polishing table20such that the movement paths of all the points on the polishing table20draw a circle with a specified radius.

The base101is placed on a work floor via a pedestal100in which a rubber vibration isolator is embedded. The base101is a plate-shaped member having a flat mounting surface (reference surface)101a, for example, with long and short sides of 300 mm×250 mm. The base101may employ a stone surface plate which is excellent in wear resistance and corrosion resistance and is deformed less by heat than general metals such as cast steel and aluminum alloys. Although the flatness necessary for the mounting surface101aof the base101depends on the number and the arrangement interval of optical connectors1that are polished at the same time, in general it only needs a precision better than class 2 of JIS (Japanese Industrial Standards). If the linear expansion coefficient of the material composing the base101is 1.1×10−5/° C. or less, metals such as cast iron, stainless steel SUS430, 50% nickel steel, or ordinary steel may be employed for the base101. Note that the pedestal100is provided with a cover140for covering a motor and a power transmission system for the motor, located adjacent to the base101, and this cover140has, at its upper portion, an operation unit141including various buttons and indicator lamps and an emergency stop switch142.

On the mounting surface101aof the base101, the polishing jig200is held by the support bases130at a certain height position. The leg portions201of the polishing jig200are clamped by toggle clamps131on the support bases130, and the polishing jig200is fixed at certain positions on the support bases130by pulling levers132. The polishing table20moves being driven by the driving mechanism120along guide members112provided on the upper surfaces of support members111of the support mechanism110. In other words, the polishing table20which is supported and driven by the support mechanism110and the driving mechanism120moves relative to the polishing jig200in a horizontal direction. This movement of the polishing table20relative to this polishing jig200polishes the connection end surfaces11cof the ferrules11of the optical connectors1held by the polishing jig200.

FIG.3is a perspective view of the outer appearance of the polishing jig200from an upper direction,FIG.4is a perspective view the outer appearance of the polishing jig200from a bottom face direction, andFIG.5is a perspective view of a fixation plate204attached to the upper surface of a cylinder base (housing)202and attachments210housed in the cylinder base202.FIG.6is a cross-sectional view of the polishing jig200inFIG.5taken along line VI-VI. The polishing jig200has the cylinder base202which is laterally elongated and the attachments210for fixing the ferrules11of the optical connectors1to the cylinder base202. Both ends of the cylinder base202in the longitudinal direction each have a leg portion201at its lower portion for fixing the cylinder base202to the support bases130of the polishing apparatus and a handle203at its upper portion. The cylinder base202has multiple cavities208that pass through from the bottom surface, and an attachment210is fitted into each of these multiple cavities208from the bottom surface of the cylinder base202. On the upper surface of the cylinder base202is the fixation plate204which has holes corresponding to the multiple cavities, and the fixation plate204is fixed to the cylinder base202using fixing means such as screws205from above.

The attachment210has a configuration in which a cylinder shaft (shaft)212is connected to a set block211with a bolt213such that the cylinder shaft212extends vertically. The cylinder shaft212has a two-stage structure having a small diameter portion and a large diameter portion, and the upper end of the small diameter portion is connected to a screw206. Around the small diameter portion of the cylinder shaft212is fitted a spring207, which is held between the lower surface of the fixation plate204and a step surface between the small diameter portion and the large diameter portion of the cylinder shaft212.

When the attachment210is pushed up, and the pushing force exceeds the elastic force of the spring207, the spring207contracts, and the screw206moves up together with the cylinder shaft212. When the force in the upper direction becomes smaller than the elastic force of the spring207, the spring207expands until the upper surface of the fixation plate204and the screw206come into contact with each other. Thus, the cylinder shaft212can reciprocate within limits, inside the cavity208of the cylinder base202.

FIGS.7and8are perspective views of the outer appearance of the attachment210.FIG.7illustrates the state where a lever215is lowered, andFIG.8illustrates the state where the lever215is raised. The set block211further has an anti-rotation (yawing) shaft214attached to extend vertically as with the cylinder shaft212. The anti-rotation shaft214is also inserted into the cylinder base202to prevent the attachment210from rotating relative to the cylinder base202(in the yawing direction).

The set block211has a rectangular hole (opening)220that passes through from the upper surface to the lower surface and through which the ferrule11of the optical connector1can be inserted. The ferrule11is inserted with the ferrule end-surface11cfacing down from the upper surface side of the set block211. On both sides of the rectangular hole220in the set block211, wall portions222are formed partially. The wall portions222holds a rotation shaft221for rotatably supporting the lever215on the set block211. The lever215rotates on the rotation shaft221such that a pushing end portion215amoves toward the rectangular hole220(in the pitching direction).

Inside the rectangular hole220in the set block211are provided a rectangular inner piece216for fixing the optical connector1to the set block211by pressing the ferrule11to a side wall of the rectangular hole220and a screw217for adjusting the pressing force of the rectangular inner piece216.

FIGS.9to12are diagrams for explaining the first to fourth steps for fixing the optical connector1to the set block211of the attachment210. InFIGS.9to12, some parts of the attachment210are illustrated as cross-sectional diagrams. With reference toFIGS.7to12, a method of fixing the optical connector1to the set block211of the attachment210will be described.

First, in the first step, the ferrule11of the optical connector1is inserted into the rectangular hole220in the set block211as illustrated inFIGS.7and9. In this process, the ferrule11is inserted with the end surface11cdirected downward the brim11adirected upward. In other words, the ferrule11is set upside down compared to the one inFIG.1. Since the ferrule11has the brim11aformed wider than the other portion, and the width of the rectangular hole220in the set block211is smaller than the width of the brim11aportion, the brim11acomes into contact with the upper surface (adjoining surface) of the set block211on both sides of the rectangular hole220due to gravity, and the ferrule11does not further enter the rectangular hole220.

Next, in the second step as illustrated inFIG.10, the operator rotates and presses the lever215so that the pushing end portion215apushes the ferrule11into the rectangular hole220, that the upper surface of the brim11acomes into close contact with the upper surface of the set block211, and that the ferrule11is pressed and fixed. In this state, the ferrule11is positioned in the rotation direction around the x-axis (rolling direction: seeFIG.7).

In the third step, the screw217connected to the rectangular inner piece216is tightened from the state illustrated inFIG.10, so that the rectangular inner piece216is pressed against the ferrule11. The pressed rectangular inner piece216in turns presses the ferrule11to the inner wall of the rectangular hole220positioned on the far side in the x-axis direction. As a result of the third step, as illustrated inFIGS.8and11, the pressed ferrule11is sandwiched between the inner wall of the rectangular hole220and the rectangular inner piece216and fixed to the set block211. Since the screw217is tighten with the ferrule11pushed by the lever215as described above, the ferrule11is not only pressed and fixed in the state where the ferrule11is positioned in the rotation direction around the x-axis (rolling direction: seeFIG.7) but also positioned in the rotation direction around the y-axis (pitching direction: seeFIG.7). As a result, the ferrule11is fixed in the rectangular hole220in the set block211in the state where the ferrule11is positioned in both directions: the rotation direction around the x-axis (seeFIG.7) and the rotation direction around the y-axis (seeFIG.7). As shown in a two-dot chain line ofFIG.7, a slope formed on the upper surface of the set block211on both sides of the rectangular hole220makes it possible to fix the ferrule11in a tilted orientation, and adjust the finished tilt angle of the ferrule end-surface11c.

After the ferrule11is fixed, the lever215may be returned to its original position as the fourth step as illustrated inFIG.12. Thus, the optical connector1is fixed at the ferrule11to the set block211of the attachment210.

The ferrule11is fixed to the set block211in the rotation direction around the x-axis (rolling direction) and the rotation direction around the y-axis (pitching direction), and the set block211is fixed to the cylinder base202also in the rotation direction around the z-axis (yawing direction) by means of the anti-rotation shaft214extending from the set block211. In addition, since the contraction and expansion of the spring207allows the cylinder shaft212to reciprocate (move up and down in the example illustrated in the diagram) inside the cavity208of the cylinder base202, the force that the end surface of the ferrule11fixed to the set block211receives from the polishing table20is kept constant.

FIGS.13A to13Ceach are a perspective view of the outer appearance of an example of a rectangular inner piece for fixing the ferrule11to the attachment.FIG.14is a perspective view of the outer appearance of the screw217for pressing the rectangular inner piece against the ferrule11to fix the ferrule11.

A rectangular inner piece illustrated inFIG.13Ahas a ferrule contact surface231athat comes into contact with a long side surface of the ferrule11and a screw receiving portion232that receives the screw217from the opposite side from the ferrule contact surface231a. In this specification, a “long side surface of the ferrule11” means a surface including a long side of the ferrule end-surface, of the four side surfaces of the ferrule11. Further, in this specification, “the lateral direction of the ferrule contact surface231a” and “the lateral direction of the long side surface of the ferrule11” mean the same direction in the state where the ferrule11is fixed to the set block211in the fourth step, and the direction that those directions mean is the same direction as the longitudinal direction which is approximately the polishing direction. In the rectangular inner piece illustrated inFIG.13A, the ferrule contact surface231ahas a round shape only in the center portion in the lateral direction (the direction indicated by the double-headed arrow inFIG.13A), thus, a protrusion231apis formed. With this configuration, when the ferrule11is fixed, the force is intensively applied only to the center portion in the lateral direction of the long side surface of the ferrule11.

A rectangular inner piece illustrated inFIG.13Bhas a ferrule contact surface231bthat comes into contact with a long side surface of the ferrule11and a screw receiving portion232that receives the screw217from the opposite side from the ferrule contact surface231b. The rectangular inner piece illustrated inFIG.13Bhas a surface protruding in the shape of a letter T in the state where the portion closer to the brim11ain the longitudinal direction of the ferrule11is directed upward (in the direction indicated by the arrow inFIG.13B). Also with this configuration, when the ferrule11is fixed, the pressure is intensively applied only to the center portion in the lateral direction of the long side surface of the ferrule11. This T-shaped protruding surface is formed flat, thus, a protrusion231bpis formed. The reason why the protruding surface is formed in the shape of a letter T instead of a letter I in the case where the protruding surface is formed flat is that if it is formed in the shape of a letter I, the center portion in the lateral direction of the long side surface of the ferrule11receives an extremely intensified pressure, and that this may break the ferrule11.

A rectangular inner piece illustrated inFIG.13Chas a ferrule contact surface231cthat comes into contact with a long side surface of the ferrule11and a screw receiving portion232that receives the screw217from the opposite side from the ferrule contact surface231c. In the rectangular inner piece illustrated inFIG.13C, the ferrule contact surface231chas a round shape in whole formed in the lateral direction (the direction indicated by the double-headed arrow inFIG.13C), thus, a protrusion231cpis formed. With this configuration, when the ferrule11is fixed, the force is intensively applied only to the center portion in the lateral direction of the long side surface of the ferrule11.

The screw217illustrated inFIG.14is a screw217for fixing the ferrule11to the set block211by pushing (pressing) the rectangular inner piece216(216a,216b,216c) against the ferrule11. The screw217has one end having a thread, which is engaged with a thread formed in the set block211, and the screw217is tightened by the engagement. When the screw217is tightened, the screw217moves pushing the ferrule contact surface231a,231b, or231cof the rectangular inner piece216toward a long side surface of the ferrule11.

FIG.15Ais a diagram illustrating the state of the long side surface of the ferrule11before and after polishing is performed with the ferrule pressed by a rectangular inner piece used in the polishing jig of the present embodiment, andFIG.15Bis a diagram illustrating the state of the long side surface of the ferrule11after polishing is performed using the polishing jig of the present embodiment, and then the pressing by the rectangular inner piece is cancelled.FIG.16is a diagram illustrating the state of the ferrule before and after polishing is performed in the state where the ferrule is held without being pressed,FIG.17Ais a diagram illustrating the state of the long side surface of the ferrule11before and after polishing is performed in the state where the long side surface of the ferrule11is pressed by a conventional rectangular inner piece, andFIG.17Bis a diagram illustrating the state of the long side surface of the ferrule after polishing is performed using the conventional polishing jig, and the pressing by the rectangular inner piece is cancelled. InFIGS.15A,16, and17A, the position of the ferrule end-surface11cbefore polishing is depicted with a solid line, and the position of the ferrule end-surface11c′ after polishing is depicted with a dashed line. The distribution of the pressing force shown as the density of points is illustrated next to the long side surface of the ferrule11.FIGS.15A and17Aillustrates the distribution of the pressing force shown as the density of points, next to the long side surface of the ferrule11.

For the polishing jig of the present embodiment, as illustrated inFIG.15A, the density of points indicating the pressing force is high in the center portion in the lateral direction (in the longitudinal direction which is the polishing direction) of the long side surface of the ferrule11. In other words, since the rectangular inner piece216(216a,216b,216c) according to the present embodiment is thicker in the center portion in the lateral direction than in the other portions, the distribution of the pressure to the ferrule11is larger in the center portion in the lateral direction (the direction indicated by the double-headed arrow inFIG.15A) than in the other portions. The ferrule end-surface11c, as illustrated inFIG.15A, is slightly deformed so as to swell in the center portion in the lateral direction (the direction indicated by the double-headed arrow inFIG.15A) where the pressing force is large. If polishing is performed in such swelling state, the swelled center portion tends to be polished more.

Also in general, in the case where the ferrule end-surface11cis polished with the polishing table20(seeFIG.2), both side portions of the ferrule end-surface11cin the lateral direction first come into contact with the polishing table20, and thus, both side portions of the end surface11cin the lateral direction tend to be polished more than the other portions. For example, in the case where the ferrule end-surface is polished with the ferrule11held without pressure to the long side surface, instead of using the polishing jig of the present embodiment, round portions are caused by polishing at both ends of the ferrule end-surface11c′ in the finishing state as illustrated inFIG.16(a round shape indicated by R1).

Thus, in the case where the ferrule end-surface11cis polished with the ferrule11pressed with the rectangular inner piece216according to the present embodiment, not only the center portion but also both side portions in the lateral direction on the ferrule end-surface11ccan be polished equally. As a result, the ferrule end-surface11c′ can be finished to be flat as illustrated inFIG.15B.

Meanwhile, for the rectangular inner piece of a conventional polishing jig, the density of points indicating the pressing force is uniform as illustrated inFIG.17A. Specifically, since the surface of the conventional rectangular inner piece that comes into contact with the ferrule11is formed to be flat, the pressing force is uniform also in the lateral direction (the direction indicated by the double-headed arrow inFIG.17A). In the case where the pressing force to the long side surface of the ferrule11is uniform in the lateral direction (the direction indicated by the double-headed arrow inFIG.15A), both side portions in the lateral direction swell more than the center portion in the ferrule end-surface11cbefore polishing, as illustrated inFIG.17A. Thus, because both side portions of the ferrule end-surface11cin the lateral direction, which originally tend to be polished more, are made likely to be polished more than the center portion, the ferrule end-surface11c′ after polishing has a round shape indicated by R2as illustrated inFIG.17B. This round shape of R2not only includes not only the round portions at both ends (the round shape of R1) illustrated inFIG.16but also includes the amount of deformation added because the ferrule end-surface11cis deformed such that both side portions swell due to the pressing force (the state where both ends are protruded), the ferrule end-surface11cis polished to be flat in this state, and after the pressure is cancelled and the deformation disappears, both side portions recess (the state where both ends are recessed).

Thus, the polishing jig of the present embodiment makes it possible to polish the ferrule end-surface11cflat with high precision, compared to the case where the ferrule11is held without pressure to the long side surface or the case where the ferrule11is held with a conventional rectangular inner piece.

Although the description in the above embodiment is based on an example in which the cylinder shaft212is formed to have a small diameter portion at its upper portion, at which one spring207is provided, the present invention is not limited to this example. The configuration only requires that an excess force applied to the set block211in the upward direction can be released by the reciprocating movement of the cylinder shaft212, and that the pressure applied to the end surface of the ferrule11is constant.

Although the description in the above embodiment is based on an example in which the shapes of the rectangular hole220, the rectangular inner piece216, and the like are rectangular, the present invention is not limited to this example. In addition, although the description is also based on an example in which the cylinder base202has a laterally elongated shape be able to receive multiple cylinder shafts, the number of cylinder shafts that can be received and the shape of the cylinder base202are not limited to this example. Other constituents are also not limited to the ones in the above embodiment, but it is obvious that those constituents can be of various forms as far as the present invention exhibits its effects.

REFERENCE SIGNS LIST