Question

Photonics and Optical Revision Sheet 1 1. Caculate the photon energy in eV for a wavelength of 1.55 um 2, A 1.55 μm digital communications system operating at 4 GBits/s receives an average power of -24 dBm at the detector. On the assumption that 1 and 0 bits are equally likely to occur how many photons are received within each 1 bit? 3. A1.3 um digital communications system operating at 3 GBits/s receives an average power of -29 dBm at the detector. Assuming that 1 and 0 bits are equally likely to occur how many photons are received within each 1 bit? 4. Describe the operating principle behind an Erbium Doped Fiber Amplifier (EDFA). 5. You are required to design an optical communications system between two locations 300 km apart. The power transmitted is O dBm and the receiver sensitivity is-29 dBm. The attenuation coefficient for the cable is 0.24 dB/kom and there is a splice every 4 km with a loss of 0.1 dB per splice. If the connector loss is 0.2 dB explain how you would incorporate an optical amplifiers into your design to ensure the correct operation of this system. Describe the different types of dispersion in an optical fiber Discuss how a Bragg Grating can be used to compensate for dispersion. A 1550 nm optical link uses a standard single-mode fiber with dispersion parameter of 4 ps/nm/km (Chromatic Dispersion), and a laser source with a linewidth of O.S nm. Assuming the link carrier is a 10 Gbits/s binary signal, estimate the maximum length of optical fiber required before dispersion compensation is required. (Assume the maximum spread is half the time interval between each bit). A step-index multimode glass fibre, with a core diameter of S0 μm and cladding refractive index of 1.45, is designed to limit the intermodal dispersion to 10ns/kom. 6. 7. 8. 9, Find its acceptance angle Calculate the maximum bit rate for transmission over a distance of 20 km. a. b.

Answer 1

Br = ISS.um E= 1.2互

exat =-24dBm 14 photm.

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