In order to generate a stable and pure 60GHz millimeter-wave signal, a periodically wavelength-swept lightwave signal over a limited wavelength range which center wavelength at 1310nm and frequency-swept rate up to 1GHz is an important component of the whole system. In this paper, we focus on three methods to yield the wanted periodically wavelength-swept lightwave signal, which are sinusoidal wavelength scan, triangular wavelength scan and saw-toothed wavelength scan. We analyze in theory the power characteristics and the spectrum characteristics of the 60GHz millimeter-wave signals relative to the different wavelength-swept lightwave signal generated by different wavelength-swept methods. Furthermore, we simulate the 60GHz radio-over-fiber transmission systems respectively with the three wavelength sweep methods and gain the results in agreement with the analysis in theory.
Our researches are based on such a system architecture that is intended to utilize the good characteristic of the interaction between millimeter-wave and lightwave to implement the 60GHz short millimeter-wave broadband wireless access system over fiber links. The networks include fiber optic links between the center stations (CS) and the base stations (BSs) and millimeter-wave air channel between the BSs and the networks terminals. The polymer optical fiber (POF) is deployed as optical fiber link medium due to its marked competitiveness in short haul, large capability communication systems. In this paper, we focus on suppressing dispersion of the radio-over-fiber transmission system. The POF is a dominant fiber chromatic dispersion source, which behaves multi-mode properties and produces inter-mode dispersion to heavily cause the POF bandwidth degradation. We present analysis on modal dispersion characteristics of 60 GHz short millimeter-wave broadband wireless access system over polymer optical fiber (POF) transmission link and present our scheme, which chooses proper launch condition to control the number of low-order modes and high-order modes excited in the POF link to improve system dispersion characteristic.
Ethernet passive optical network (EPON), which represents the convergence of low-cost, high-bandwidth and supporting multiple services, appears to be one of the best candidates for the next-generation access network. The work of standardizing EPON as a solution for access network is still underway in the IEEE802.3ah Ethernet in the first mile (EFM) task force. The final release is expected in 2004. Up to now, there has been no standard application specific integrated circuit (ASIC) chip available which fulfills the functions of media access control (MAC) layer of EPON. The MAC layer in EPON system has many functions, such as point-to-point emulation (P2PE), Ethernet MAC functionality, multi-point control protocol (MPCP), network operation, administration and maintenance (OAM) and link security. To implement those functions mentioned above, an embedded real-time operating system (RTOS) and a flexible programmable logic device (PLD) with an embedded processor are used. The software and hardware functions in MAC layer are realized through programming embedded microprocessor and field programmable gate array(FPGA). Finally, some experimental results are given in this paper. The method stated here can provide a valuable reference for developing EPON MAC layer ASIC.