An apparatus and method for producing optical pulses of a desired wavelength utilizes a section of higher-order-mode fiber to receive input optical pulses at a first wavelength, and thereafter produce output optical pulses at the desired wavelength through soliton self-frequency shifting or Cherenkov radiation. The shoe roll includes a flexible, replaceable press cover having two end regions and at least one end supporting disc. For example, the entities may be separated by a distance of less than about 1000 nm, or less than about 300 nm for visible light.