Multimode Optical Fiber Trench Core Bandwidth

The patent converts the harmful radiation modes into beneficial cladding modes by introducing a low-refractive-index trench region. The trench structure causes higher-order modes to couple into the cladding, transforming what would be lossy radiation modes into guided cladding modes that propagate along the fiber axis, thereby reducing transmission losses while maintaining the simple core-clad structure for easy splicing.

The patent applies local quality by introducing a trench region with distinct refractive index properties at a specific location (peripheral region of the core). This localized modification creates a potential well that traps higher-order modes, allowing different regions of the fiber to have different functional characteristics without changing the overall fiber structure.

The patent converts manufacturing errors in the refractive index profile into a beneficial feature by intentionally creating a trench region with lower refractive index. This trench structure acts as a mode-selective potential well that compensates for profile deviations, causing higher-order modes to couple into the cladding even when the core profile is imperfect, thereby maintaining bandwidth without requiring high manufacturing precision.

The patent changes the refractive index parameter by introducing a trench region with a distinct refractive index value different from both the core and cladding. This parameter modification creates a new optical potential that modifies mode propagation characteristics, making the system less sensitive to manufacturing variations in the core profile.

The patent converts harmful higher-order modes with large differential group delays into beneficial cladding modes by using the trench structure as a coupling mechanism. The trench creates a potential well that guides these modes along the fiber axis in the cladding region, transforming them from time-dispersive radiation modes into guided modes that maintain phase coherence, thereby enabling multimode transmission with reduced differential group delays.

The trench region acts as an intermediary structure between the core and cladding, facilitating the coupling of higher-order modes from the core into the cladding. This intermediate layer modifies the optical potential to enable controlled mode transfer, allowing higher-order modes to propagate in the cladding with reduced differential group delays compared to direct core propagation.