opto-sim is a modular headless Python library for simulating real-world optical systems at a backend level. It models components like lasers, LiNbO₃ phase modulators, beam splitters, fiber cables, and APDs, using numerical methods and Stokes vector polarization analysis. Think of it as a lightweight, scriptable backend akin to what powers tools like HFSS, Lumerical, or SIwave—minus the GUI.

Work in Progress
This project is under active development and not production-ready, but reflects:

• A strong interest in engineering simulation
• Hands-on application of numerical methods to physical systems
• A backend-first approach suitable for scripting, automation, and scientific use
• Emphasis on physics-first modeling, internal APIs, and extendability.

This simulator aims to mimic the behavior of physical optical components used in QKD experiments—specifically BB84 protocol setups—through mathematical models. It’s intended as a learning tool and experimental platform for simulating realistic noise conditions, signal degradation, and quantum encoding/decoding via optics.

• Laser Source

  • Solid-state lasers modeled after Nd:YAG and Er:YAG systems.

• Phase Modulators

  • Supports X-cut and Y-cut, Z-propagating configurations.

• Avalanche Photodiodes (APDs)

  • Models include shot noise, thermal noise, and random Gaussian/Poisson noise.

• Optical Components

  • Basic tools like beam splitters, couplers, etc

• Visualization

  • Polarimetry
  • Calculation of Stokes parameters for polarization state analysis.
  • Poincare Sphere

• Fiber Cable

  • Simulates fiber transmission, optional dispersion modeling

All models aim to closely reflect published experimental setups and component behaviors found in academic literature. While accuracy is a priority, simplifications are made when necessary to keep computations tractable.

• Physics-first architecture: Built from experimental papers and known equations
• Modular backend API: Easily compose system-level simulations
• Pure Python + NumPy stack
• Runs in Jupyter/Colab with reproducible outputs and examples
• Output includes:
  • Stokes vector breakdown
  • Cosine similarity across transmission
  • Realistic phase and polarization transitions

from src.opto_eq import PhaseModulator
from src.lasers import sslaser as laser
from src.viewers.stokes import compute_stokes_parameters
from src.viewers import polarimeter
source = laser.SolidStateLaser(
    wavelength=1550e-9,  # Laser wavelength
    polarization_azimuth=np.pi,  # 45° polarization
    polarization_ellipticity=np.pi/4,
    power_dbm=-5,  # arbitrary power unit
    frequency=5e6
)
E_field = source.get_electric_field(normalize=False, over_period=True)
S0, S1, S2, S3 = compute_stokes_parameters(E_field)
print(f"S0 = {S0:.3f}\nS1 = {S1:.3f}\nS2 = {S2:.3f}\nS3 = {S3:.3f}")
polarimeter(E_field, title=f"Laser Output")
pm = PhaseModulator(crystal_cut='X', modulation='DC')
E_modulated = pm.modulate(E_field, V=3.3)
S0, S1, S2, S3 = compute_stokes_parameters(E_modulated)
print(f"S0 = {S0:.3f}\nS1 = {S1:.3f}\nS2 = {S2:.3f}\nS3 = {S3:.3f}")
polarimeter(E_modulated, title=f"Phase Modulator Output")

S0 = 0.910
S1 = 0.000
S2 = -0.707
S3 = -0.707

S0 = 0.910
S1 = 0.000
S2 = 0.951
S3 = 0.309

• numpy
• scipy
• matplotlib

Install dependencies with:

pip install -r requirements.txt

🚫 This simulator is intended for demonstration and research purposes only. Please contact me for permission before using in personal research/projects or commercial projects.

• Feel free to reach out via GitHub issues or messages if you’re curious about the project and want to collaborate.