Image Number 3 for United States Patent #6570652.
A device for monitoring wavelength division multiplexed optical signals for use in an optical network and in an optical performance monitor. A device has a structure for supporting components of the device. An optical component is supported at one end of the structure for transmitting the optical signals. A diffraction grating is supported at an opposing end of the structure for diffracting the optical signals from the optical component. An optical sensor is supported in relation to the diffraction grating by the structure for monitoring the optical signals. A telephoto lens assembly is supported by the structure and disposed between the optical sensor and the diffraction grating, the lens assembly having a focal length for focusing the optical signals in relation to the optical sensor. Thermal effects on the structure are balanced against thermal effects on the lens assembly. A prism is disposed between the lens assembly and diffraction grating. The prism is configured to anamorphically compress the diffracted optical signals. Thermal effects on the diffraction grating are balanced against thermal effects on the lens and prism.