The BB-500-11-1300/1550-62.5/125-M-35-XX-3-1-ND from OZ Optics Ltd. is a Fiber Optic Attenuator with Wavelength Dependent Loss <0.3 dB, Attenuation Up to 40 dB, Insertion Loss <0.6 to 1.5 dB, Return Loss 35 dB, Operating Wavelength 1300 nm, 1550 nm. More details for BB-500-11-1300/1550-62.5/125-M-35-XX-3-1-ND can be seen below.