Gain equalizer, collimator with gain equalizer and method of manufacturing gain equalizer

A collimator connected to first and second single-mode optical fibers and having a gain equalizer for flattening a gain spectrum of an optical amplifier for amplifying a multiplexed optical signal having optical signals with a plurality of different wavelengths multiplexed, the gain spectrum having a gain peak, the gain peak having a peak wavelength, the gain equalizer comprising:

• a minus filter including an incident side collimator lens for converting light output from the first single-mode optical fiber to parallel light and a dielectric multilayer filter formed on a surface of the incident side collimator lens,
• a reception side collimator lens, adhered to a surface of the dielectric multilayer filter, for coupling the parallel light to the second single-mode optical fiber,
• the dielectric multilayer filter including a first dielectric thin film formed on the surface of the incident side collimator lens and a second dielectric thin film formed on the first dielectric thin film,
• wherein both the first dielectric thin film and the second dielectric thin film have refractive indexes, and wherein the difference between the refractive index of the first dielectric thin film and the refractive index of the second dielectric thin film is relatively small so that the dielectric multilayer filter has a reflection characteristic for reflecting an optical signal of a predetermined wavelength band including the peak wavelength of the gain spectrum.

A method of manufacturing a gain equalizer, comprising the steps of:

• preparing a transparent base;
• forming a first dielectric thin film by depositing a first metal material on a surface of the transparent base by physical vapor deposition;
• forming a second dielectric thin film by depositing a second metal material having a composition slightly different from a composition of the first metal material on a surface of the first dielectric thin film by physical vapor deposition;
• and
• forming a dielectric multilayer filter by alternately depositing a plurality of first dielectric thin films and a plurality of second dielectric thin films on the surface of the transparent base.

A method of manufacturing a gain equalizer, comprising the steps of:

• preparing a transparent base;
• forming a first dielectric thin film by depositing a first metal material oil a surface of the transparent base by chemical vapor deposition;
• forming a second dielectric thin film by depositing a second metal material having a composition slightly different from a composition of the first metal material on a surface of the first dielectric thin film by chemical vapor deposition;
• and
• forming a dielectric multilayer filter by alternately depositing a plurality of first dielectric thin films and a plurality of second dielectric thin films on the surface of the transparent base.

A method of manufacturing a gain equalizer, comprising the steps of:

• preparing a transparent base;
• arranging at least one electrode on the transparent base;
• forming a first dielectric thin film by supplying power to the at least one electrode to deposit at least one kind of a first metal material on a surface of the transparent base by sputtering;
• forming a second dielectric thin film by supplying power to the at least one electrode to deposit at least one kind of a second metal material on a surface of the first dielectric thin film by sputtering;
• and
• wherein the first and second dielectric thin films have refractive indexes that are different from each other.