Ethernet physical layer PHY Medium

The Ethernet PHY layer of a predetermined signal, connectors and cables required, the physical layer can be divided into PCS / PMA / PMD layer. The following illustrates a figurative physical layer. The following sections describe in detail the properties of Medium.

2.1.1 Fast Ethernet

Fast Ethernet is mainly defined in the 802.3 section-2 Clause 21

100BASE-TX

100BASE-TX available for transmission, and two pairs of shielded twisted pair or two or more of a class of 5 unshielded twisted pair in the two media. Supports full duplex mode, the maximum transmission distance of 100 meters, the transmission lines of 1/2, 3/6 receives, using RJ45 connectors.

The PCS uses 4B / 5B coding mode, the signal frequency of 125MHz.

100BASE-T4

3 above four pairs of unshielded twisted pair using 100BASE-T4. Site using three pairs of data transmission lines, ½, 4/5, 7/8, 3/6 using a pair of lines to detect conflicts. Site receiving data using 3/6, 7/8, 4/5 three pairs of lines.

100BASE-T4 encoding uses 8B / 6T, each group of eight 6-bit image three yuan symbols, and each symbol has a potential of 3 (+, 0, -), and therefore there are available codewords 729 ( 3 ^ 6), but to represent all combinations of the 8-bit word can be as long as 256 kinds (2 ^ 8) is then in turn transmits the output of the three output lines, each line of the baud rate is 25M baud as 25M baud / 6 * 8 = 33.33Mbps, so that the total transmission rate of 100Mbps.

100BASE-FX

100BASE-FX using two strands of optical fiber, for transmitting data wherein an surge for receiving data, to support full duplex mode, the available single mode fiber or multimode fiber. Using MIC / FDDI connector, ST connector or SC connector.

Use of 4B / 5B-NRZI encoding, the signal frequency of 125MHz.

2.1.2 Gigabit Ethernet

1000BASE-T

1000BASE-T can Category 5 unshielded twisted pair, the maximum effective distance of 100M. 1000T user employs techniques may be implemented to smooth upgrade from 1000Mbps 100Mbps Fast Ethernet in the original system.

1000Base-T uses 4 pairs of lines for bidirectional transmission, support full duplex communication.

由于同一传输方向上使用2对线，因此网络设备需要串扰/回声消除技术。

编码方式PAM-5

1000BASE-LX (long wavelength laser)

使用长波激光作为信号源，工作波长为1310nm.使用SC连接器。

采用8B/10B编码方式，运行速率为1250Mbaud.

1000BASE-SX(short wavelength laser)

使用短波激光作为信号源，工作波长为850nm, 使用SC连接器。

采用8B/10B编码方式，运行速率为125MBaud.

1000BASE-CX(short-haul copper)

采用150Ω平衡屏蔽双绞线，使用两种类型的连接器，9芯D型连接器连接电缆，和