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--- rb:sfp [26/09/2025 10:07] – [SFP module (Small Form-factor Pluggable)] andrew
+++ rb:sfp [09/06/2026 09:16] (current) – [Multimode Fibre] andrew
@@ Line 59: / Line 59: @@
 ----
 ===== Multimode Fibre =====
+Just a look inside for interest...
 {{:rb:sfp_152322.jpg?200 |}}
@@ Line 64: / 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 |