Power insensitive stable isolator wavelength division multiplexer

An apparatus, comprising:

• an isolator wavelength division multiplexer (IWDM) comprising a WDM-Isolator core;
• a signal-fiber optically coupled to a first side of the WDM-Isolator core, the signal-fiber configured to propagate signal light;
• a pump-fiber defining an expanded tip optically coupled to a second side of the WDM-Isolator core, the pump-fiber configured to propagate pump light;
• and
• a common-fiber optically coupled to the second side of the WDM-Isolator core, the common-fiber configured to propagate a combination of the signal light and the pump light;
• wherein the WDM-Isolator core is configured to transmit the signal light to the common-fiber and to reflect the pump light into the common-fiber;
• wherein the pump-fiber comprises a core portion and a cladding portion, wherein the core portion defines a first diameter over a portion of its length and a second diameter at a fiber end-face optically coupled to the WDM-Isolator core, wherein the second diameter is greater than the first diameter to define the expanded tip;
• wherein the common-fiber comprises a core portion and a cladding portion, wherein the core portion defines a single diameter over a portion of its length including a fiber end-face optically coupled to the WDM-Isolator core;
• and
• wherein the signal-fiber comprises a core portion and a cladding portion, wherein the core portion defines a single diameter over a portion of its length including a fiber end-face optically coupled to the WDM-Isolator core.

An apparatus, comprising:

• an isolator wavelength division multiplexer (IWDM) comprising a WDM-Isolator core;
• a first fiber optically coupled to the WDM-Isolator core, the first fiber configured to propagate light at a first wavelength;
• a second fiber defining an expanded tip optically coupled to the WDM-Isolator core, the second fiber configured to propagate light at a second wavelength;
• and
• a third fiber optically coupled to the WDM-Isolator core, the third fiber configured to propagate a combination of the light at the first wavelength and the light at the second wavelength;
• wherein the WDM-Isolator core is configured to transmit the light at the first wavelength to the third fiber and to reflect the light at the second wavelength into the third fiber.