Next-generation MOST PHY with 1Gbit/s keeping today's optoelectronics and fiber: Page 3 of 6

May 31, 2012 // By Norbert Weber, Conrad Zerna, Fraunhofer IIS
Next-generation MOST PHY with 1Gbit/s keeping today's optoelectronics and fiber
The optical version of the MOST physical layer has several well-known advantages. It has virtually no EMI problems. The SI-POF has low weight and the fiber and optoelectronics are low-cost. As the need for higher data rates grows, the feasability of the next generation of MOST on the currently attractive link components becomes an urgent topic. The article describes the Physical Layer for future Gigabit MOST.

of 10-4 before into 10-12 after the FEC. The block code nature of the decoder is also capable of supressing propagated errors in the feedback structure of the DFE; no error bursts were measured. Project partner ISMB [6] did this part of the work and implemented a demonstrator on an FPGA platform. Due to the additional recoding of the Gigabit Ethernet data, which reduced the net data rate by 12%, the ISMB was able to achieve a 50m link with 7dB of optical margin [7].

So, in summary, the result of POF-Plus are two 50m demonstrations applying equalization and (in the second case) error correction and achieving error-free transmission with (in the second case) significant margin. When the improved components are used, the compensation of the fiber bandwidth alone results in only a small insertion loss of the equalizer (see below).

Integration of new results into Power Budget Calculations

The worst case in the power budget of MOST150 is described [8] as: an averaged transmitted power of -8.5dBm with an extinction ratio of 10dB, a coupling loss of 2.5dB at transmitter and receiver, an additional coupling loss for two inline connectors of 2dB each and a receiver sensitivity of -22dBm. This results, with an effective attenuation of 0.4dB/m, in a fiber of 11.2m length (see Table 1 below).

During the extension of the power budget to the optical physical layer of next generation MOST, we were making the following adjustments.

First of all, we left the parameters for LED wavelength range and spectral width unchanged. This results in the same effective POF attenuation. We did also not speculate about any improvements of the coupling in the inline connectors.

We have changed these parameters: We removed the TX coupling loss, because the driver prototypes were characterised in an FOT package in fiber coupled power. The coupling loss at the RX is higher because of the smaller photo diode and misalignment errors.

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