Patent ID: 11867576
Assignee: PETROLIAM NASIONAL BERHAD (PETRONAS)
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. An optical cable for measuring a stress wave generated by vibration of a measurement target, the optical cable comprising:
a stress wave detection optical cable including an optical fiber provided at an axial part, a plurality of first steel wires helically wound so as to surround the optical fiber, and a flexible material surrounding the optical fiber and the plurality of first steel wires; and
second steel wires different from the first steel wires, wherein
the stress wave detection optical cable and the second steel wires are helically wound to form one annular body as a whole, and
a winding angle (α) of the stress wave detection optical cable with respect to an axis of the optical cable is a function of a strain ratio parameter (A), wherein the strain ratio parameter (A) is a function of two Lamé constants (λ, μ),
each of said Lamé constants (λ, μ) being a function of an elastic moduli (E) and a Poisson's ratio (ν) of the flexible material and a cable surrounding body surrounding the optical cable at a location where the optical cable is placed;
wherein:, A
   =
   
    2
    ⁢
    
     tan
     2
    
    ⁢
    α
   
  
  ,
  
   A
   =
   
    
     
      λ
      0
     
     +
     
      2
      ⁢
      
       μ
       0
      
     
    
    
     λ
     +
     
      2
      ⁢
      μ
     
    
   
  
  ,
  
   E
   =
   
    
     μ
     ⁡
     (
     
      
       3
       ⁢
       λ
      
      +
      
       2
       ⁢
       μ
      
     
     )
    
    
     (
     
      λ
      +
      μ
     
     )
    
   
  
  ,
  
   v
   =
   
    
     λ
     
      2
      ⁢
      
       (
       
        λ
        +
        μ
       
       )
      
     
    
    .