Interlocked n-by-n wavelength selective switch

A method of selectively passing or simultaneously adding and dropping optical signals according to wavelength, the method comprising:

• receiving input optical signals via an optical input array comprising an express in port and N add ports;
• providing an optical output array comprising an express out port and N drop ports, the N drop ports and the N add ports forming N add-drop pairs, each of the N add-drop pairs including an add port of the N add ports and a corresponding drop port of the N drop ports;
• using a passive system to diffract the input optical signals to form diffracted optical signals and focusing the diffracted optical signals onto an array of switching elements;
• controlling the array of switching elements to reflect the diffracted optical signals and form reflected optical signals;
• and
• using the passive optical system to focus the reflected optical signals onto the optical output array,
• wherein the add port and the corresponding drop port of each add-drop pair are arranged relative to the express in port and the express out port such that input optical signals can be simultaneously reflected, by one of the switching elements via the passive optical system, both from the add port to the express out port and from the express in port to the corresponding drop port.

A method of making an interlocked N×N wavelength selective switch (WSS), the method comprising:

• forming an optical input array comprising an express in port and N add ports;
• forming an optical output array comprising an express out port and N drop ports, the N drop ports and the N add ports forming N add-drop pairs, each of the N add-drop pairs including an add port of the N add ports and a corresponding drop port of the N drop ports;
• providing an array of switching elements;
• and
• arranging a passive optical system configured to diffract the input optical signals to form diffracted optical signals, focus the diffracted optical signals onto the array of switching elements, receive reflected optical signals from the array of switching elements, and focus the reflected optical signals onto the optical output array,
• wherein forming the optical input array forming the optical output array comprises arranging each add port and the corresponding drop port of each add-drop pair, relative to the express in port and the express out port, such that input optical signals can be simultaneously reflected, by one of the switching elements via the passive optical system, both from the add port to the express out port and from the express in port to the corresponding drop port.