Cisco GBICs

Hi;
I have some confusion on fibre GBICs, I understand the following are used for the fibre handoff.

GLC-SX-MMD      1000BASE-SX SFP transceiver module, MMF, 850nm, DOM
GLC-LH-SMD      1000BASE-LX/LH SFP transceiver module, MMF/SMF, 1310nm, DOM

Can single mode be used for multimode Gbic. Also, do every vendor has its own Gbic. We have Ciena 3930 and was wondering if Cisco gbic can be used?? Please supply all the information about the GBICs as I want to understand it in its entireity.

Thanks
totaramAsked:
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mikebernhardtCommented:
You can't use single mode with multimode GBIC because the core diameter is different and you will lose a lot of light. sometimes it will work if the distance is not too long but don't count on it.

A GBIC is a GBIC as long as the specs are correct. Some vendors like Cisco require it to be programmed with their info or their equipment will complain. But most will work with a Cisco-programmed or else generic GBIC.
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totaramAuthor Commented:
I did not get the core diameter part.. if GLC-LH-SMD is used on both ends.. is there a way for the gbics to know it is being used on smaller distance?
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Sajid Shaik MSr. System AdminCommented:
read about the single and multi mode :

https://en.wikipedia.org/wiki/Multi-mode_optical_fiber

Single mode SFP's to use with single mode optic fiber only and multi mode for multi mode cable only,
may be in future it'll come's with dual face.

you can use GLC-LH-SMD, the distance is not a big issue,

see the cisco document :

http://www.cisco.com/c/en/us/products/interfaces-modules/1000base-lx-lh-sfp/index.html

Cisco's industry-standard SFP is a hot-swappable input/output device that plugs into a Gigabit Ethernet port/slot, linking the port with the fiber-optic network. SFPs can be used and interchanged on a wide variety of Cisco products and can be intermixed in combinations of IEEE 802.3z- compliant 1000BaseSX, 1000BaseLX/LH, or 1000BaseZX interfaces on a port-by-port basis.

The Cisco GLC-LH-SM fully complies with the IEEE 802.3z 1000BaseLX standard. However, their higher optical quality allows them to reach 10 km over single-mode fiber (SMF) versus the 5 km specified in the standard.

here is the document on specific distance related:
http://www.cisco.com/c/en/us/products/collateral/interfaces-modules/gigabit-ethernet-gbic-sfp-modules/product_data_sheet0900aecd8033f885.html

all the best
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totaramAuthor Commented:
Thanks Shaik;
I understand the links that you sent and get the big picture here. I howver have two questions:
1. The core diameter mentioned above, is this the diameter of the tube where the light travels .. it is mentioned something like 62.5 micro meters?
2. The wiki link talks of the higher wavelength for MM and the lower wavelength for SM. But as per the GBIC documentation, the MM wavelength is 850 NM and SM wavelength is 1310 NM, can you please explain that? Not sure, if they are talking of the freq. rather than wavelength.
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Sajid Shaik MSr. System AdminCommented:
Greetings,

i seen your interest in subject to understand the concept..... really I appreciate it... here is documentation...

Fiber Optic Network Optical Wavelength Transmission Bands


As fiber optic networks have developed for longer distances, higher speeds and wavelength-division multiplexing (WDM), fibers have been used in new wavelength ranges, now called "bands," where fiber and transmission equipment can operate more efficiently. Singlemode fiber transmission began in the "O-band" just above the cutoff wavelength of the SM fiber developed to take advantage of the lower loss of the glass fiber at longer wavelengths and availablility of 1310 nm diode lasers. (Originally SM fibers were developed for 850 nm lasers where the fiber core was about half what it is for today's conventional SM fiber (~5 microns as opposed to ~8-9 microns at 1310 nm.)

see this article :
http://www.thefoa.org/tech/ref/basic/SMbands.html

here is the complete guide for fiber optics
http://www.thefoa.org/tech/ref/contents.html

i hope u'll get all the answers, in detail...

all the best
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mikebernhardtCommented:
1. The core diameter mentioned above, is this the diameter of the tube where the light travels .. it is mentioned something like 62.5 micro meters?
The core diameter for multimode is either 62.5 micrometers (older) or 50 micrometers (newer). This is the diameter of the actual glass through which the light travels. For single mode fiber it is 8.25 micrometers.

2. The wiki link talks of the higher wavelength for MM and the lower wavelength for SM. But as per the GBIC documentation, the MM wavelength is 850 NM and SM wavelength is 1310 NM, can you please explain that? Not sure, if they are talking of the freq. rather than wavelength.
I don't really understand your question. NM is wavelength, as I'm sure you know wavelength and frequency are inversely proportional.

3. I did not get the core diameter part.. if GLC-LH-SMD is used on both ends.. is there a way for the gbics to know it is being used on smaller distance?
No. what I meant was that if the core diameter and the GBICs don't match up then there will be a lot of loss, both because of the size mismatch (light getting lost because either the LED is bigger than the glass or vice versa) as well as differing characteristics of the fiber. But if the distance is short (a few hundred meters maybe?), running multimode GBICs with single mode fiber can still work despite the loss. I would not recommend it though.
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