Methods and apparatus for preventing deadbands in an optical communication system

An apparatus for a wavelength division multiplexed optical communications system comprising:

• an optical circulator having a first port, a second port, and a third port, said optical circulator configured such that optical signals which are received by said first port of said optical circulator are routed to said second port of said optical circulator, and optical signals which are received by said second port of said optical circulator are routed to said third port of said optical circulator;
• an optical filter including a first port, a second port, a third port and characterized by a falling edge deadband wavelength range, said optical filter configured such that optical signals corresponding to said deadband wavelength range which are received by said first port are not substantially transmitted to said second port or said third port;
• and
• an optical communications path connecting said second port of said optical circulator to said second port of said optical filter, said optical communications path including at least one grating configured such that optical signals of said falling-edge deadband wavelength range are reflected to said third port of said optical circulator.

A multiplexing/demultiplexing apparatus for a wavelength division multiplexed optical communications system comprising:

• a first optical circulator including a first port, a second port, and a third port, said first optical circulator configured such that optical signals which are received by said first port of said first optical circulator are output through said second port of said first optical circulator, and optical signals which are received by said second port of said first optical circulator are output through said third port of said first optical circulator;
• a first optical filter including a first port, a second port, and a third port configured such that optical signals corresponding to a deadband wavelength range received by said first port are not substantially passed to either said second port or said third port, optical signals corresponding to a first wavelength range received by said first port are substantially passed to said second port, and optical signals of a second wavelength range are substantially passed to said third port;
• a first optical communications path connecting said second port of said first optical circulator to said first port of said first optical filter, said first optical communications path including at least one first grating adapted to reflect optical signals substantially corresponding to said deadband wavelength range received from said second port of said first optical circulator;
• a second optical filter including a first port, a second port, and a third port configured such that optical signals corresponding to said deadband substantially passed to said second port, optical signals corresponding to said first wavelength range received by said first port are passed to said second port, and optical signals corresponding to said second wavelength range received by said third port are passed to said second port;
• a second optical communications path connecting said second port of said first optical filter and said first port of said second optical filter;
• a second optical circulator including a first port, a second port, and a third port, said second optical circulator configured such that optical signals which are received by said first port of said second optical circulator are transmitted to said second port of said second optical circulator, and optical signals which are received by said second port of said second optical circulator are transmitted to said third port of said second optical circulator;
• a third optical communications path connecting said second port of said second filter to said second port of said second optical circulator, said third optical communications path including at least one second grating adapted to reflect said deadband wavelength range received from said second port of said second optical circulator;
• and
• a fourth optical communications path connecting said third port of said first optical circulator and said first port of said second optical circulator.

A multiplexing/demultiplexing apparatus for a wavelength division multiplexed optical communications system comprising:

• a first optical circulator including a first port, a second port, and a third port, said first optical circulator configured such that optical signals which are received by said first port of said first optical circulator are exit through said second port of said first optical circulator, and optical signals which are received by said second port of said first optical circulator are exit through said third port of said first optical circulator;
• a first optical filter including a first port, a second port, and a third port configured such that optical signals corresponding to a deadband wavelength range received by said first port are not substantially passed to either said second port or said third port, optical signals corresponding to a first wavelength range received by said first port are substantially passed to said second port, and optical signals of a second wavelength range are substantially passed to said third port;
• a first optical communications path connecting said second port of said first optical circulator to said first port of said first optical filter, said first optical communications path including at least one first grating adapted to reflect optical signals substantially corresponding to said deadband wavelength range received from said second port of said first optical circulator;
• a second optical filter including a first port, a second port, and a third port configured such that optical signals corresponding to said deadband wavelength range which are received by said first port are not substantially passed to said second port, optical signals corresponding to said first wavelength range received by said first port are passed to said second port, and optical signals corresponding to said second wavelength range received by said third port are passed to said second port;
• a second optical communications path connecting said second port of said first optical filter and said first port of said second optical filter;
• an optical coupler including a first port, a second port, and a third port, said optical coupler configured such that optical signals received by said first port of said optical coupler are combined with optical signals received said second port and transmitted to said third port;
• a third optical communications path connecting said second port of said second filter to said first port of said optical coupler;
• and
• a third optical communications path connecting said third port of said first optical circulator and said first port of said second optical circulator.