You are tasked with connecting a new pair of hosts to an existing SAN infrastructure. The existing infrastructure is a 2Gb/s Fibre Channel solution…

When connecting new hosts to an existing 2Gb/s Fibre Channel SAN, several physical layer concerns are critical. Option (C) is a major concern because mixing multimode fibers with different core diameters (50µm and 62.5µm) in the same link causes significant signal loss and modal distortion, which can lead to link failure. Option (B) is a concern because relying solely on signal strength (dB) ignores other distance-limiting factors like modal dispersion, which degrades the signal quality over length, regardless of power. Fibre Channel standards specify maximum distances for each fiber type and speed for this reason. Option (D) is a concern because it is based on the false premise that Gigabit Ethernet and Fibre Channel cabling are interchangeable; they are different technologies with distinct physical layer requirements.

A. The measured bit error rate (BER) is between "1 in 10^16" and "1 in 10^15"

This is not a concern. The Fibre Channel standard requires a BER of 10^-12 or better. A measured BER of 10^-15 is exceptionally good and indicates a very high-quality link.

1. For option C (Mixing Fiber Types):

Robert, K. (2009). Fibre Channel for SANs. Cisco Press. In Chapter 3, "Fibre Channel Media," it is explained that "Mixing 62.5-micron and 50-micron fiber-optic cables in the same link is not recommended. Significant loss of optical power can occur, which can cause the link to fail." This principle is fundamental to optical network design.

2. For option B (Cable Lengths and Signal Strength):

Clark, T. (2009). Designing Storage Area Networks (2nd ed.). Addison-Wesley Professional. In Chapter 4, "Fibre Channel Physical Variants," Table 4-1 specifies the maximum distance for 2Gbps FC over 62.5µm MMF as 300 meters and over 50µm MMF as 500 meters. The text explains these limits are due to factors including modal dispersion, not just the optical power budget (loss). Relying only on a power measurement is insufficient.

3. For option D (Re-using Ethernet Cable):

Stallings, W. (2016). Data and Computer Communications (10th ed.). Pearson. Chapter 26, "Storage Area Networks," describes Fibre Channel as a distinct protocol from Ethernet (covered in Chapter 15). The physical and data link layers are entirely different, making their cabling infrastructure and components (transceivers, switches) non-interchangeable without adhering to specific cross-protocol standards like FCoE, which is not implied here.

4. For option A (Bit Error Rate):

INCITS. (2005). Fibre Channel - Physical Interfaces - 2 (FC-PI-2), Rev 8.0. T11/1322-D. Section 5.4, "Bit error ratio," states, "The bit error ratio (BER) at the ingress to a port shall be less than 10^-12." A value of 10^-15 or 10^-16 is significantly better than this requirement and therefore not a concern.