Differences

This shows you the differences between two versions of the page.

--- rb:sfp [10/09/2025 13:15] – [WDM Fibre] andrew
+++ rb:sfp [09/06/2026 09:16] (current) – [Multimode Fibre] andrew
@@ Line 1: / Line 1: @@
 ====== SFP module (Small Form-factor Pluggable) ======
-SFP modules followed on from [[rb:gbic|GBIC]] modules and are used in both ethernet and fibre channel switches (and others too), they are usually optical I/O modules although RJ45 copper Ethernet ones are available. Ethernet modules are most commonly 1GB/s but 10GB/s and higher are available. SFP used for Fibre channel can be 1 or 2GB/s but most common is 4GB/s.
+SFP modules followed on from [[rb:gbic|GBIC]] modules and are used in both ethernet and fibre channel switches (and others too), they are usually optical I/O modules although RJ45 copper Ethernet ones are available. Ethernet modules are most commonly 1GB/s but 10GB/s and higher are available.
+SFP used for Fibre channel can be 1 or 2GB/s but most common is 4GB/s.
@@ Line 31: / Line 33: @@
 Another option is Wavelength Division Multiplex SFP which use two different wavelength for Tx and Rx, so only needing one fibre. This example uses SC single mode ( SC == Stick 'n' Click )
+----
+{{ :rb:single-bidirectional-fibre.jpg?400 |}}
 ----
@@ Line 51: / Line 57: @@
+----
+===== Multimode Fibre =====
+Just a look inside for interest...
 {{:rb:sfp_152322.jpg?200 |}}
@@ Line 56: / Line 66: @@
 {{:rb:sfp_152240.jpg?200 |}}
+My guess is that the Single mode SFP are very similar to the Multi Mode, although the lasers may be more powerful due to the extended range for Single Mode, possibly bigger or have a heatsink?
+----
+===== SFP commands - IOS =====
+Specific to Cisco IOS as SFPs can be found in Fibre Channel SAN switches and other manufacturer's kit.
+Inserting a SFP module
+<code>
+router01#
+*Nov 30 19:44:22.751: %EHWIC_1GE_SFP_CU-6-SFP_INSERTED: Transceiver module 1000BaseSX SFP is inserted in GigabitEthernet0/0/0 interface.
+</code>
+This is in a [[networking:cisco-1921|Cisco 1921 Gigabit router]] with a WIC for gigabit copper and and SFP module.
+<code>
+router01#sh inventory
+NAME: "CISCO1921/K9", DESCR: "CISCO1921/K9 chassis, Hw Serial#: FCZ1625C5YF, Hw Revision: 1.0"
+PID: CISCO1921/K9      , VID: V04 , SN: FCZ1625C5YF
+NAME: "Enhanced High Speed WAN Interface Card-1 Port Gigabit Ethernet SFP/Cu on Slot 0 SubSlot 0", DESCR: "Enhanced High Speed WAN Interfa"
+PID: EHWIC-1GE-SFP-CU  , VID: V01, SN: FOC15164VRP
+NAME: "1000BASE-SX SFP", DESCR: "1000BASE-SX SFP"
+PID:  , VID:    , SN: FNS1007Q4PF
+</code>
+Cisco 2960 series switch, this shows two inserted sfp, neither of which is connected to fibre, hence very low optical power on Rx.
+<code>
+x-1#sh interfaces transceiver
+If device is externally calibrated, only calibrated values are printed.
+++ : high alarm, +  : high warning, -  : low warning, -- : low alarm.
+NA or N/A: not applicable, Tx: transmit, Rx: receive.
+mA: milliamperes, dBm: decibels (milliwatts).
+                                 Optical   Optical
+           Temperature  Voltage  Tx Power  Rx Power
+Port       (Celsius)    (Volts)  (dBm)     (dBm)
+---------  -----------  -------  --------  --------
+Gi1/0/25     36.0       3.38      -5.0     -40.0
+Gi1/0/26     32.5       3.33      -5.1     -40.0
+</code>
+| Tx Power (dBm) | Transmit optical power | –9 to –3 dBm | Too low = failing laser or dirty connector |
+| Rx Power (dBm) | Receive optical power  | –20 to –3 dBm | Too low = excessive fiber loss / bad patch |