### pypho v3

#### pypho_fiber

The fiber class models the transmission of an optical signal along a fiber.

For this the non linear Schrödinger equation is solved numerically by the Fourier-Split-Step-Method:

$$\frac{\partial A_x }{\partial x} + \beta_{1x} \frac{\partial A_x }{\partial t} + \frac{j\beta_{2} }{2} \frac{\partial A_x }{\partial t^2} -\frac{\beta_{3} }{6} \frac{\partial A_x }{\partial t^3} + \frac{\alpha }{2}A_x = i\gamma\left( |A_x|^2 + \frac{2}{3}|A_y|^2 \right)A_x$$ $$\frac{\partial A_y }{\partial x} + \beta_{1y} \frac{\partial A_y }{\partial t} + \frac{j\beta_{2} }{2} \frac{\partial A_y}{\partial t^2} - \frac{\beta_{3} }{6} \frac{\partial A_y }{\partial t^3} + \frac{\alpha }{2}A_y = i\gamma\left( |A_y|^2 + \frac{2}{3}|A_x|^2 \right)A_y$$

Both polarisations and their interaction are calulated. You cannot "switch" one polarisation off, to reduce the calculation time.

pypho_fiber.__init__(glova, fibertype, D, S, gamma, alpha, l, birefarray, phi_max)

Instantiation and parameter setting.

Parameter Type Description
glova instance Global parameters
fibertype string Sets default values for typical fiber types:
'SSMF': D=17, S=17, alpha=0.2
D float Dispersion coefficient at the center frequency pypho_setup.f0 in $\frac{\text{ps}}{\text{nm km}}$.
S float Dispersion slope coefficient in $\frac{\text{ps}}{\text{nm}^{2} \text{km}}$.
gamma float Nonlinear coefficient $\gamma$ in $\frac{1}{\text{W km}}$.
alpha float Fiber attenuation $\alpha$ in $\frac{\text{dB}}{\text{km}}$.
l float Fiber length in km.
birefarray list This list describes the polarisation properties of the fiber. The list must include a rotation angle birefarray[].angle the fiberlength birefarray[].z_point and a $\Delta\beta_1 = \beta_{1x} - \beta_{1y}$ value birefarray[].delta_beta valid to the next of the birefarray[].z_point.

Output Type Description
User defined variable pypho_fiber.pypho_fiber

pypho_fiber.__call__(E, fibertype (optional), D (optional), S (optional), ...
...gamma (optional), alpha (optional), l (optional), ...
...birefarray (optional), phi_max (optional))

Parameter Type Description
E list List in which the optical data and noise signal are defined. Read here about data signal and noise representation
Optional paramter   As defined above

Output Type Description
User defined variable list Returns a list in which the optical data and noise signal are defined. Read here about data signal and noise representation.