Patent ID: 6920270

Claim:
A method for determining at least one parameter of a periodic spin function α(z) with period p, to be applied to an optical fibre along its length z, comprising: selecting said at least one parameter so that  ∫ 0 p ⁢ y 1 ⁡ ( z , α ′ ⁡ ( z ) ) ⁢ ⁢ ⅆ z  ∫ 0 p ⁢  y 1 ⁡ ( z , α ′ ⁡ ( z ) )  ⁢ ⅆ z ≤ ɛ 1 where ε 1 is about 0.05 and y 1 is the first of the three components y 1 (z), y 2 (z), y 3 (z) of a periodic function {overscore (y)}(z) of a period p such that ⅆ y 1 ⅆ z = 2 ⁢ α ′ ⁡ ( z ) ⁢ y 2 ⅆ y 2 ⅆ z = - 2 ⁢ π L B ⁢ y 3 - 2 ⁢ α ′ ⁡ ( z ) ⁢ y 1 ⅆ y 3 ⅆ z = 2 ⁢ π L B ⁢ y 2 where L B is an expected beat length of said optical fibre and α′(z) is the derivative of the spin function α(z) with respect to the length z.