Multiwavelength Erbium-Doped Random Fiber Laser for Parallel Physical Entropy and Image Encryption

High quality physical randomness is essential for secure information processing, random bit generation, and image encryption, while wavelength-parallel entropy generation provides an effective route to increasing the number of available physical random channels. In this work, we develop an all fiber, dual-end-pumped, dual section erbium-doped random fiber laser (ERFL) by combining distributed Rayleigh feedback with intracavity Sagnac spectral filtering. The laser generates 24 wavelength channels over an approximately 6.7-nm spectral range. Synchronously measured intensity fluctuations are evaluated across all 276 distinct channel pairs using the repeat-averaged absolute zero-delay Pearson correlation coefficient. The median coefficient is 0.0052, with 98.2% of the channel pairs at or below 0.02. Mutual-information analysis further supports weak nonlinear dependence between the wavelength channels. The intensity sequences obtained from different wavelength channels are further used to derive physical key material for authenticated image encryption and decryption. The representative ciphertext exhibits a near-uniform gray-level histogram and weak adjacent-pixel correlations, while authenticated decryption with the correct key recovers the original image exactly. These results demonstrate a 24-channel, low cross correlation, all fiber ERFL platform for wavelength-parallel physical entropy generation and information security applications.