Copper Cables and Connectors

Active vs Passive cables

• Active cables are copper cables for data transmission that use a silicon chip (semiconductor) to boost the performance of the cable. Without a chip, a cable is considered a 'passive' cable. 
• Passive cables are liable to degrade the data they carry, due to such "channel impairments" as attenuation, crosstalk and group velocity distortion. 
• In active cables, one or several semiconductor chips are embedded in the cable to compensate for some or all of these impairments. 
• This active boosting allows cables to be more compact, thinner, longer and transmit data faster than their passive equivalents. 
• While passive cables are always copper-based, active cables can use either copper wire or fiber optics to provide the link between the cable ends.

Why Twinax is used instead of RJ-45?

• There are two types of Copper Cabling- Twinax and RJ45 Ethernet (Cat6 or higher) 
• For Twinax cabling, the connector is SFP+ and for UTP cat6 cables, the connector used is RJ-45 
• The twinax cable uses a different signal propagation method, my understanding is that it’s more like a radio wave than an electrical signal. A UTP signal needs a lot of electronics to drive generate and receive the signal. 
• The end result is that Twinax uses much less power (something around 1 – 1.5W per port) compared to UTP (4 – 6 W per port). When you have a lot of ports this power consumption can be significant factor in design. 
• Twinax is an ideal 10GbE solution for server to Top of Rack switch connection. Since it uses less power and is more reliable that UTP solution as the cable is physically more robust and not subject to physical damage, an important consideration for 10GbE over copper. Any damage to the copper cable due to crushing or bending can cause intermittent failures on Cat6 cabling (although less likely on Cat6A). 
• But the main reason for choosing twinax for 10GbE is lower power consumption for server to top of rack connections for integrated storage and data networks.

TYPES OF COPPER CABLES:

UTP Cable:
- As the name suggests, this type of cable includes an unshielded media that includes twisted pairs.
- Specifically, UTP includes four different pairs of copper cables that are each twisted together
- The twisted rate depends on the specific category of cable- can be cat5e, cat6, cat6a and better the quality, higher the distance

- It is the most used copper cable which has 4 pairs of copper cables twisted together

STP Cable
- Another type of twisted pair cabling includes a shield that is used to both contain and protect the different twisted pairs from interference. 

- This type of cabling is not commonly seen in modern LAN networks.

- Similar to UTP, but, the pairs are shielded to prevent interference. This is very rare in modern lan environments, but, is still used where high speed low-interference is needed.

- In your daily life, where have you seen any shielded cable? Yes, the one which is used for your cable TV- coaxial cables are shielded

TYPES OF CONNECTORS FOR COPPER:

RJ45-The cable connector that is found on almost all UTP and STP cables is a Registered Jack 45 which is mostly commonly referred to as RJ45.
-RJ45 cables have 8 color-coded wires, and the plugs have 8 pins and conductors. Eight wires are used as 4 pairs, each representing positive and negative polarity.

RJ-45 Straight-Through and Cross-Over connections:

We have seen about what straight-through and cross-over means in this post: http://heartofnetworking.blogspot.com/2018/05/straight-through-and-cross-over-cables.html 

We can make these cables in copper with RJ-45 connectors as shown below:

TRANSCEIVERS:

- We can usually connect the RJ-45 ports into regular RJ-45 jacks on our laptops

- But, on most new switches, it is not possible since the switches do not come with RJ-45 ports

- In such scenarios, we need to use something called as 'Transceivers' which convert the signals from RJ-45 cables into a form that the switch's ports will understand...Think of it like a translator which translates from one language to another.

- Also, most modern switches are designed for both optical and copper. So, they will not be restricted to onlyRJ-45. All modern switches and routers will have something called as SFP/QSFP ports. So, if we want to connect a RJ-45 copper cable to that port, we need to use a SFP transceiver called SFP-1G-T which has SFP ((male) port on one side and RJ-45 jack (female) on another side. We could also use the same SFP port to connect an optical fiber, just by changing the transceiver to one which supports optical connector like LC or SC/ST

SFP-1G-T

Do cables and ports speak the same language?

Transceivers essentially translate the signals from the cable into a form which the switch can understand. Mostly, switches will have SFP/QSFP ports on them. So, for a optical cable, if we use a transceiver, it will translate the light signals to electrical signs for the switch. Similarly, if we use a copper cable, we can use a transceiver for that and connect it to the same port on the switch.

TWINAX CABLES:

- Also, known as DAC cables (Directly attached Copper)

- In datacenter environments, they are used more often than RJ-45 or other UTP cables.

Reasons for DAC cables are used in datacenters much more than UTP/RJ-45?

• It has SFP connectors attached to copper, so no need to use transceivers...you can save cost of transceivers. 
• Second, UTP cables consume lot of power (around 4-6 W per port) whereas twinax cables use much less power (1-1.5 W per port). When you consider hundreds of thousands of ports, this cost saving is significant 
• Also, this cable is more robust than UTP cables and is not subject to physical damage upon bending which prevents loss

10G SFP+ Copper Twinax cable