Method of determining likelihood of optical fiber connector making positive contact
View Patent ↗A method of qualifying a ferrule assembly as being adequate to make physical contact upon mating, the method comprising approving the ferrule assembly if an undercut of the ferrule assembly does not exceed a maximum allowable undercut based on ferrule deformation at a particular compressive load and apex offset.
1. A method of qualifying a ferrule assembly as being adequate to make physical contact upon mating, said ferrule assembly comprising a ferrule having an end face and at least one fiber in said ferrule, said method comprising:
measuring the following parameters of said ferrule assembly;
fiber undercut;
radius of curvature of said end face; and
apex offset from the center of said fiber in said ferrule assembly;
qualifying said ferrule assembly if said fiber undercut is less than said maximum fiber undercut, said maximum fiber undercut complying with the following equation:
u ( R ,δ)= C·R β −R+√{square root over (R 2 −δ 2 )}
where,
u=said maximum fiber undercut,
R=said end face radius of curvature,
C=a constant related to compressive force,
β=a constant related to a given ferrule material, and
δ=said apex offset.
2. The method of claim 1 , wherein maximum allowable undercut is also based on differences in thermal expansion between said fiber and said ferrule.
3. The method of claim 2 , wherein maximum allowable undercut is represented by the following equation:
u ( R ,δ)= C·R β −R+√{square root over (R 2 −δ 2 )}−α·Δ T
where,
α=differential coefficient of thermal expansion which is material dependant, and
ΔT=temperature difference.
4. The method of claim 3 , wherein maximum allowable undercut is a function of creep.
5. The method of claim 4 , wherein maximum allowable undercut is represent by the following equation:
u ( R,δ,k )= C·R β −R+√{square root over (R 2 −δ 2 )}−α·Δ T−k
where,
u=maximum allowable fiber undercut,
R=end face radius of curvature,
β=a constant related to ferrule material,
C=a constant related to compressive force,
δ=apex offset from fiber center,
α=differential coefficient of thermal expansion,
ΔT=upper application temperature, and
k=permanent fiber withdrawal.
6. The method of claim 1 , wherein said ferrule assembly is approved even if it does not meet the GR326-Core, Issue 3 specification.
7. The method of claim 6 , wherein a ferrule assembly having a radius of curvature greater than 30 mm is approved.
8. The method of claim 6 , wherein a ferrule assembly having an apex offset greater than 50 μm is approved.
9. A lot of approved terminated connector assemblies comprising:
a plurality of connectors, each connector having a ferrule assembly containing one or more fibers, one or more ferrule assemblies of said lot being outside standards set forth in GR326-Core, Issue 3 specification, but having an undercut that does not exceed a maximum allowable undercut wherein said maximum allowable undercut is represented by the following equation
u ( R ,δ)= C·R β −R+√{square root over (R 2 −δ 2 )}
where,
u=maximum allowable fiber undercut,
R=end face radius of curvature,
C=a constant related to compressive force,
β=constant related to a given ferrule material, and
δ=apex offset from fiber center.
10. The lot of claim 9 , wherein maximum allowable undercut is represented by the following equation:
u ( R ,δ)= C·R β −R+√{square root over (R 2 −δ 2 )}−α·Δ T−k
where,
α=differential coefficient of thermal expansion which is material dependant, and
ΔT=temperature difference.
11. The lot of claim 9 , wherein said one or more ferrule assemblies have a radius of curvature greater than 30 mm.
12. The lot of claim 9 , wherein one or more ferrule assemblies have an apex offset greater than 50 μm.
13. An apparatus for determining whether a ferrule assembly is qualified for making physical contact when mated, said ferrule assembly comprising a ferrule having an end face and at least one fiber in said ferrule, said apparatus being configured to perform the following steps:
obtaining the following parameters of said ferrule assembly:
fiber undercut;
radius of curvature of said end face; and
apex offset from the center of said fiber in said ferrule assembly; and
qualifying said ferrule assembly if said fiber undercut is less than said maximum fiber undercut, said maximum fiber undercut complying with the following equation:
u ( R ,δ)= C·R β −R+√{square root over (R 2 −δ 2 )}
where,
u=said maximum fiber undercut,
R=said end face radius of curvature,
C=a constant related to compressive force,
β=a constant related to a given ferrule material, and
δ=said apex offset.
14. The apparatus of claim 13 , wherein said apparatus is a non-contact inter ferometer, and the step of obtaining the parameters of said ferrule assembly comprises measuring said parameters.
15. The apparatus of claim 13 , wherein said apparatus is a stand-alone computer in which said parameters are inputted.
16. The apparatus of claim 15 , wherein said apparatus is interfaced with a non-contact interferometer and receives said parameters therefrom.