Tunable light source and optical module

A tunable light source, comprising:

• a light source;
• a wavelength selecting device that selects, according to a control signal, output light with a specific wavelength from light output from the light source;
• a wavelength monitor including
• a wavelength filter including multiple output ports corresponding to filtering paths through which the output light passes, and
• at least one light-receiving device that is disposed to face one of the output ports and receives light output from the one of the output ports;
• and
• a controller that generates the control signal based on a quantity of the light received by the light-receiving device such that the wavelength of the output light matches a target wavelength, and outputs the generated control signal to the wavelength selecting device, wherein
• the wavelength filter is configured such that a maximum quantity of the light output from the one of the output ports that faces the light-receiving device becomes greater than a maximum quantity of light output from another one of the output ports that does not face the light-receiving device;
• the output ports comprise two or more output ports;
• the wavelength filter includes
• a splitter that splits the output light into first light and second light,
• a first waveguide through which the first light passes,
• a second waveguide through which the second light passes, the first waveguide and the second waveguide having different lengths, and
• an optical divider that combines the first light and the second light input from the first waveguide and the second waveguide, splits the combined light into two or more light beams, and outputs the light beams to the two or more output ports;
• and
• the optical divider is configured to split the combined light such that maximum quantities of the light beams become different from each other.

An optical module, comprising:

• a tunable light source;
• and
• an optical modulator that modulates output light output from the tunable light source and outputs the modulated light,
• wherein the tunable light source includes
• a light source,
• a wavelength selecting device that selects, according to a control signal, the output light with a specific wavelength from light output from the light source,
• a wavelength monitor including
• a wavelength filter including multiple output ports corresponding to filtering paths through which the output light passes, and
• a light-receiving device that is disposed to face one of the output ports and receives light output from the one of the output ports, and
• a controller that generates the control signal based on a quantity of the light received by the light-receiving device such that the wavelength of the output light matches a target wavelength, and outputs the generated control signal to the wavelength selecting device;
• and
• wherein the wavelength filter is configured such that a maximum quantity of the light output from the one of the output ports that faces the light-receiving device becomes greater than a maximum quantity of light output from another one of the output ports that does not face the light-receiving device;
• the output ports comprise two or more output ports;
• the wavelength filter includes
• a splitter that splits the output light into first light and second light,
• a first waveguide through which the first light passes,
• a second waveguide through which the second light passes, the first waveguide and the second waveguide having different lengths, and
• an optical divider that combines the first light and the second light input from the first waveguide and the second waveguide, splits the combined light into two or more light beams, and outputs the light beams to the two or more output ports;
• and
• the optical divider is configured to split the combined light such that maximum quantities of the light beams become different from each other.