1000BASE-ZX GBIC Question

I have purchased two 1000BASE-ZX GBICs for use on a run of SMF over which LX
GBICs did not work.

Cisco.com recommends the use of attenuators for runs less than 25 km. I have
the attenuators and will test the link using them first. If the link does
not work with the attenuators, is it safe to test the link without the
attenuators? i.e. can the GBICs be damaged by too powerful a light source
being inputted into the rx side?

From cisco.com:

The Cisco 1000BASE-ZX GBIC (WS-G5487) operates on ordinary single-mode fiber
optic link spans up to 43.4 miles (70 km) long. Link spans of up to 62 miles
(100 km) are possible using premium single-mode fiber or dispersion shifted
single-mode fiber. The GBIC provides an optical link budget of 23 dB-the
precise link span length will depend on multiple factors such as fiber
quality, number of splices, and connectors.

When shorter distances of single-mode fiber are used, it might be necessary
to insert an in-line optical attenuator in the link to avoid overloading the
receiver:
A 5-dB or 10-dB inline optical attenuator should be inserted between the
fiber-optic cable plant and the receiving port on the Cisco 1000BASE-ZX GBIC
at each end of the link whenever the fiber-optic cable span is less than
15.5 miles (25 km).

Many thanks for your help in advance.

Dan

 

["Daniel Conlon"]

| Cisco.com recommends the use of attenuators for runs less than 25 km. I have
| the attenuators and will test the link using them first. If the link does
| not work with the attenuators, is it safe to test the link without the
| attenuators? i.e. can the GBICs be damaged by too powerful a light source
| being inputted into the rx side?

Yes, ZX GBICs can be damaged if the attenuation is too low - they can *not*
be run back to back.

Steinar Haug, Nethelp consulting,

 

Hmmmm. Seems unlikely to me. Can you please point me to
something convincing on the web?

 

[AnyBody43]

| > Yes, ZX GBICs can be damaged if the attenuation is too low - they can *not*
| > be run back to back.
|
| Hmmmm. Seems unlikely to me. Can you please point me to
| something convincing on the web?

How about

http://www.cisco.com/en/US/products...on_guide_chapter09186a00801d5800.html#1022899

which states that the Cisco ZX GBICs have a max output power of 4.77 dBm,
and a max input power of -3 dBm?

Steinar Haug, Nethelp consulting,

 

| > Yes, ZX GBICs can be damaged if the attenuation is too low - they can
*not*

But does that mean that they will actually be damaged, or just that the link
will not work?

 

["Daniel Conlon"]

| http://www.cisco.com/en/US/products/hw/switches/ps606/products_installation_
| guide_chapter09186a00801d5800.html#1022899
| >
| > which states that the Cisco ZX GBICs have a max output power of 4.77 dBm,
| > and a max input power of -3 dBm?
|
| But does that mean that they will actually be damaged, or just that the link
| will not work?

A sufficiently high optical power level will certainly damage a GBIC in
the sense of shortening its lifetime.

Given the cost of ZX GBICs, it's much simpler to just stay within specs
and make sure you have sufficient attenuation.

Steinar Haug, Nethelp consulting,

 

| > Yes, ZX GBICs can be damaged if the attenuation is too low - they
can

Since I tried LX GBICs and they did not work, and they have a maxium output
power of -3 dBm and reciever sensitivity of -19 dBm, can I deduce from this
that the fibre run has at least a 16 dBm loss?

And assuming that is the case, can I also deduce that the maxium input power
over the run with the ZX GBICs will be -11.23dBm (4.77 - 16) and therefore I
may connect the ZX GBICs up with no risk of exceeding the maximum input
power?

 

["Daniel Conlon"]

| Since I tried LX GBICs and they did not work, and they have a maxium output
| power of -3 dBm and reciever sensitivity of -19 dBm, can I deduce from this
| that the fibre run has at least a 16 dBm loss?
|
| And assuming that is the case, can I also deduce that the maxium input power
| over the run with the ZX GBICs will be -11.23dBm (4.77 - 16) and therefore I
| may connect the ZX GBICs up with no risk of exceeding the maximum input
| power?

That sounds like a reasonable assumption if it is the attenuation
which prevents the LX GBICs from working. You could possibly also
have a faulty GBIC.

To be certain I would advise measuring the loss in the fibre.

Steinar Haug, Nethelp consulting,

 

Indeed. In the world of optical, it's extremely important not to
overload receivers.

-Terry

 

Gbic 1000Base ZX

I am also having problems with my two Cisco Gbic 1000Base ZX. I have connected them using using an 80Km run of fiber between them. the fiber had a break and i respliced the fiber and at that plice the loss is 0.003dBm and the total loss for the 80km is 28dBm.

The problem here is after respicing my Gbic can nolonger see each other. what coud be the problem. If i cconnect them on a distance of 10km they can see each other.