This value specifies the link length that is supported by the
transceiver while operating in compliance with the applicable
standards using single mode fiber. The value is in units of
kilometers. A value of 255 means that the transceiver supports
a link length greater than 254 km. A value of zero means that
the transceiver does not support single mode fiber or that the
length information must be determined from the transceiver
technology. XFP uses this object for the same purpose.