Abstract
Constraints exist for the fundamental-mode spot size for broadband dispersion-compensated fibres because of the relationship between dispersion and spot size. Dispersion compensation between 1.3 and 1.55 μm is still possible with the usual spot radius of about 5 μm at λ = 1.3 μm, while dispersion compensation between 1.3 and 1.8 μm would require a spot radius of less than 4 μm.