Cable & Hardware Reference

// ethernet · fiber · sfp · connectors · poe · speed tables

// ethernet copper cable categories

Category	Max Speed	Max Distance	Frequency	Shielding	Use Case
Cat 3	10 Mbps	100m	16 MHz	UTP	Legacy voice/10BASE-T. Obsolete.
Cat 5	100 Mbps	100m	100 MHz	UTP	FastEthernet. Replace if found.
Cat 5e	1 Gbps	100m	100 MHz	UTP/STP	Most common legacy install. Still fine for 1G.
Cat 6	1 Gbps / 10 Gbps*	100m / 55m*	250 MHz	UTP/STP	Standard new install. 10G limited to 55m.
Cat 6A	10 Gbps	100m	500 MHz	STP/SFTP	Recommended for 10G runs. Thicker cable.
Cat 7	10 Gbps	100m	600 MHz	SFTP	Not TIA/EIA ratified. GG45 connector.
Cat 8	25/40 Gbps	30m	2000 MHz	SFTP	Data centre short runs only. Very stiff.

// t568a vs t568b pinout

Pin	T568A	T568B (Most Common)	10/100 Use	Gigabit Use
1	White/Green	White/Orange	TX+	BI_DA+
2	Green	Orange	TX-	BI_DA-
3	White/Orange	White/Green	RX+	BI_DB+
4	Blue	Blue	—	BI_DC+
5	White/Blue	White/Blue	—	BI_DC-
6	Orange	Green	RX-	BI_DB-
7	White/Brown	White/Brown	—	BI_DD+
8	Brown	Brown	—	BI_DD-

T568B is most common in North America and commercial installations. Use same standard on both ends for straight-through. Crossover = T568A one end, T568B other (rarely needed with modern auto-MDIX switches).

// single-mode vs multimode

Type	Core Size	Distance	Speed	Cost	Use Case
OM1 (MMF)	62.5μm	Up to 300m	1 Gbps	Low	Legacy multimode. Orange jacket.
OM2 (MMF)	50μm	Up to 600m	1 Gbps	Low	Older multimode. Orange jacket.
OM3 (MMF)	50μm	300m @ 10G	10 Gbps	Medium	Laser-optimised. Aqua jacket. Common in DC.
OM4 (MMF)	50μm	400m @ 10G	10/25 Gbps	Medium	Improved OM3. Aqua/violet jacket.
OM5 (MMF)	50μm	400m @ 10G	Up to 100G	Medium-High	Wideband multimode. Lime-green jacket.
OS1 (SMF)	9μm	Up to 10km	10 Gbps+	High	Tight-buffer indoor SMF. Yellow jacket.
OS2 (SMF)	9μm	Up to 200km	10 Gbps+	High	Loose-tube outdoor SMF. Yellow jacket. WAN/campus.

// fiber connector types

Connector	Size	Ferrule	Common Use
LC	Small form	1.25mm	Most common in data centres and modern equipment
SC	Standard	2.5mm	Push-pull. Common in telco and older enterprise
ST	Standard	2.5mm	Bayonet lock. Legacy campus/building installs
FC	Standard	2.5mm	Screw-on. High vibration environments, telco
MPO/MTP	Multi-fibre	Multiple	12/24 fibre trunk cables. High-density DC

// sfp form factor comparison

SFP

100M / 1G

Size: Small Form-factor
Use: Standard 1G uplinks
Standard: SFF-8472

SFP+

10G

Size: Same as SFP
Use: 10G server/switch links
Note: SFP+ fits SFP+ slots only

SFP28

25G

Size: Same as SFP
Use: 25G server connections
Note: Modern DC standard

QSFP+

40G

Size: Quad SFP
Use: 40G switch uplinks
Note: 4x10G lanes

QSFP28

100G

Size: Quad SFP
Use: 100G spine/core links
Note: 4x25G lanes

QSFP-DD

400G

Size: Double density
Use: Hyperscale DC
Note: 8x50G lanes

// common sfp+ types

Type	Speed	Medium	Distance	Wavelength
SFP-T (BASE-T)	1G/10G	Copper Cat6A	30m	N/A
SX	1G	OM1/OM2 MMF	550m	850nm
LX	1G	SMF / MMF	10km / 550m	1310nm
SR (10G)	10G	OM3/OM4 MMF	300m / 400m	850nm
LR (10G)	10G	OS1/OS2 SMF	10km	1310nm
ER (10G)	10G	SMF	40km	1550nm
ZR (10G)	10G	SMF	80km	1550nm
BiDi	1G/10G	SMF (single strand)	10/40km	1310/1490nm
DAC (Direct Attach)	10/25/40/100G	Twinax copper	1-7m	N/A
AOC (Active Optical)	10/25/40/100G	MMF	Up to 100m	850nm

// physical connectors quick reference

Connector	Speeds	Use Case	Notes
RJ45	10M → 10G	Ethernet copper	8P8C. Most common network connector.
RJ11	POTS/DSL	Telephone/DSL	6P2C/6P4C. Smaller than RJ45.
LC Duplex	1G → 100G	Fiber patch	Most common fiber in modern installs.
SC Duplex	1G → 10G	Fiber patch	Push-pull. Common in older installs.
MPO-12	40G/100G	High-density fiber trunk	12 fibers. Used with QSFP breakout.
USB-C	Up to 10G	Console/management	Modern console ports on network gear.
DB9/RS-232	Serial	Console access	Legacy console port. Requires adapter.
Rollover/Console	Serial	Cisco console	Light blue RJ45 on Cisco gear. 9600 baud.

// power over ethernet standards

Standard	IEEE	Max Power (PSE)	Max Power (PD)	Pairs Used	Common Devices
PoE	802.3af	15.4W	12.95W	2 pairs	IP phones, basic APs, cameras
PoE+	802.3at	30W	25.5W	2 pairs	802.11n/ac APs, PTZ cameras, thin clients
PoE++	802.3bt Type 3	60W	51W	4 pairs	802.11ax APs, video conferencing
PoE++	802.3bt Type 4	100W	71.3W	4 pairs	Laptops, TVs, small switches
UPoE	Cisco Prop.	60W	60W	4 pairs	Cisco proprietary — high-power APs

// poe quick tips

Issue	Likely Cause	Fix
Device won't power on	Insufficient PoE budget	Check switch PoE budget — total watts allocated vs available
AP keeps rebooting	Underpowered PoE	Upgrade to PoE+ or PoE++ switch port
Works on one port, not another	Port PoE disabled or failed	Check port PoE config: show power inline (Cisco)
Cat5 cable won't do 60W PoE	Wrong cable category	PoE++ (4-pair) requires Cat5e minimum, Cat6A recommended