1000BASE-X
1000BASE-X is used in industry to refer to gigabit Ethernet transmission over fiber, where options include 1000BASE-CX, 1000BASE-LX, and 1000BASE-SX, or the non-standard -LH/-ZX/-BX10 implementations.
1000BASE-CX
1000BASE-CX is an initial standard for gigabit Ethernet connections over copper cabling with maximum distances of 25 meters using balanced shielded twisted pair. It is still used for specific applications where cabling is not done by general users, for instance the IBM BladeCenter uses 1000BASE-CX for the Ethernet connections between the blade servers and the switch modules. 1000BASE-T succeeded it for general copper wiring use.
1000BASE-LX
1000BASE-LX is a fiber optic gigabit Ethernet standard specified in IEEE 802.3 Clause 38 which uses a long wavelength laser (1270 to 1355 nm), and a maximum RMS spectral width of 4 nm.
1000BASE-LX is specified to work over a distance of up to 5 km over 10 µm single-mode fiber. In practice it will often operate correctly over a much greater distance. Many manufacturers will guarantee operation up to 10 or 20 km, provided that their equipment is used at both ends of the link.
1000BASE-LX can also run over multi-mode fiber with a maximum segment length of 550 m. For link distances greater than 300 m, the use of a special launch conditioning patch cord may be required.[2] This launches the laser at a precise offset from the center of the fiber which causes it to spread across the diameter of the fiber core, reducing the effect known as differential mode delay which occurs when the laser couples onto only a small number of available modes in multi-mode fiber.
1000BASE-SX
1000BASE-SX is a fiber opticgigabit Ethernet standard for operation over multi-mode fiber using a 770 to 860 nanometer, near infrared(NIR) lightwavelength.
The standard specifies a distance capability between 220 meters (62.5/125 µm fiber with low modal bandwidth) and 550 meters (50/100 µm fiber with high modal bandwidth). In practice, with good quality fibre and terminations, 1000BASE-SX will usually work over significantly longer distances.[citation needed]
This standard is highly popular for intra-building links in large office buildings, co-location facilities and carrier neutral internet exchanges.
Optical power specifications of SX interface: Minimum output power = -9.5 dBm. Minimum receive sensitivity = -17 dBm.
1000BASE-LH
1000BASE-LH is a non-standard but industry accepted term to refer to gigabit Ethernet transmission using 1300 or 1310 nm wavelength. It is very similar to 1000BASE-LX, but achieves longer distances up to 10 km over single-mode fiber due to higher quality optics. 1000BASE-LH is backwards compatible with 1000BASE-LX.
1000BASE-ZX
1000BASE-ZX is a non-standard but industry accepted term to refer to gigabit Ethernet transmission using 1550 nm wavelength to achieve distances of at least 70 km over single-mode fiber.
1000BASE-BX10
This latest addition to the standard also includes the 1000-BASE-BX10 transmission over a single strand of fiber (which is itself single-mode fiber), with one different wavelength going in each direction. The terminals on each side of the fibre are not equal, as the one transmitting "downstream" (from the center of the network to the outside) uses the 1490 nm wavelength, and the one transmitting "upstream" uses the 1310 nm wavelength.
1000BASE-T
1000BASE-T (also known as IEEE 802.3ab) is a standard for gigabit Ethernet over copperwiring. It requires, at a minimum "Category 5" cabling, while Category 5e cableor Category 6 cablemay also be used and is often recommended. 1000BASE-T requires all four pairs to be present and is far less tolerant of poorly installed wiring than 100BASE-TX. If two Gigabit devices are connected through a non-compliant Cat5 cable with four pairs, many FCS errors and retransmissions may occur. If two Gigabit devices are connected through a non-compliant Cat5 cable with two pairs only, negotiation takes place on two pairs only, so it ends up successfully choosing gigabit as the Highest Common Denominator (HCD), but the link never goes up. Most gigabit physical devices have a specific register to diagnose this behaviour.
Each network segment can have a maximum distance of 100 meters. Autonegotiationis a requirement for using 1000BASE-T[4] according to the standard. At least clock source has to be negotiated, as one has to be Master and the other Slave. Several physical layer devices and drivers will allow you to force 1000 Mbit/s full duplex to eliminate autonegotiation issues. In this non-standard use, the designer must assure only one peer is configured as the clock master. Forcing duplex settings or turning off autonegotiation can become a permanent choice in a large installation, because the forced node is now non-compliant. When deployed, it will mean any future ethernet switch must be forced as well. A solution is to remove or fix the non-compliant nodes, rather than making more nodes non-compliant.
1000BASE-T details
In a departure from both 10BASE-Tand 100BASE-TX, 1000BASE-T uses all four cable pairs for simultaneous transmission in both directions through the use of echo cancellation and a 5-level pulse amplitude modulation(PAM-5) technique. The symbol rate is identical to that of 100BASE-TX (125 Mbaud) and the noise immunity of the 5-level signaling is also identical to that of the 3-level signaling in 100BASE-TX, since 1000BASE-T uses 4-dimensional Trellis Coded Modulation(TCM) to achieve a 6 dBcoding gain across the 4 pairs.
The data is transmitted over four copper pairs, eight bitsat a time. First, eight bits of data are expanded into four 3-bit symbols through a non-trivial scrambling procedure based on a linear feedback shift register; this is similar to what is done in 100BASE-T2, but uses different parameters. The 3-bit symbols are then mapped to voltage levels which vary continuously during transmission. One example mapping is as follows:
