QC技术培训讲座(二)

0 dB reflection loss reflection wavelength (frequency) zero-loss reference
transmission
•
•
The peak wavelength (frequency) in transmission is defined as the wavelength (frequency) at which the minimum loss occurs in the transmission spectrum (the point closest to the zero loss reference). A peak wavelength (frequency) is typically not defined for a reflection spectrum. The minimum loss in the reflection spectrum is simply called the reflection loss. The wavelength (frequency) at which the minimum loss occurs may be called the reflection wavelength.
2006-8-25
14
Wavelength (Frequency) Definitions
ITU wavelength (frequency)
• Frequency standards have been established for DWDM products by the International Telecommunications Union (ITU). These ITU values are referenced from a frequency of 193.1 THz (1552.524 nm) with channel spacing of 0.1 THz (100 GHz). • Wavelength (l) and frequency (f) are related by: λ = 299792.458 / f
2006技术培训讲座（二）
赵强 8/24/2006
Digitally signed by Andrew Zhao DN: cn=Andrew Zhao, c=US, o=Primanex Corp., ou=Research and Development, email=Andrew. Zhao@ Reason: I am the author of this document Date: 2006.08.25 14:31:06 +08'00'
2006-8-25
5
信号传输容量/速度 (Transmission Capacity)
• Transmission Capacity: measures how much information it can carry.
– For digital systems it is the number of bits per second passing a given point. – For analog systems it is the transmission bandwidth, usually measured in MHz or GHz.
SONET OC-3 Carrier 155Mbit/s
FDDI Network 100Mbit/s
To Reconversion Stages at Receiver End
2006-8-25
9
传输格式、交换标准、光纤传输标准
• 数字信号传输格式：即如何将数字信号打包传输？
– TDM：对每个进入数据流分配固定时间槽位 – Packet Switching：将数据流分解为数据包并将其放入有空闲的时间槽位中。 每个数据包中包含数据头，指明目的地。
transmission
• The Tx IL may be defined as the maximum loss, the loss at the center of the Tx spectrum, or the maximum loss over a certain wavelength window (passband or guardband loss). • The Rx IL is typically defined as the maximum loss near the edges of the reflection spectrum.
2006-8-25
10
PON（无源光网络）
Central Office
1310nm or 1490nm
ONT
Diplexer
1310nm
Voice/Data
Triplexer
OLT Video Video Head-end 1550nm 1xN Splitter Network Voice/Data Digital OC3 & OC12 Video Analog
概要
• 对光纤通讯系统常识的进一步介绍 • 光纤通讯器件和其它领域光电子器件的常用术语
2006-8-25
2
光纤通讯系统的另一分类
• 取决于如何传输信号，光纤通讯系统又可分类为：
– – – – 点对点系统（point-to-point） 点对多点（广播式）系统（point-to-multipoint, or broadcast system） 网络系统（networked system） 开关交换系统（switched system）
2006-8-25
6
信号复（共）用技术(Multiplexing)
• 信号复用技术：将多个信号混合在一起由同一传输媒介传播。 • 信号复用技术的种类：
– 时分复用（Time-Division Multiplexing）：针对数字系统。串行排队 方式，将多个同频数据流排队进入同一数据流。 – 频分复用（Frequency-Division Multiplexing）：针对模拟系统。 – 波分复用（Wavelength-Division Multiplexing）：最大灵活性和容量/ 速率，对信号传输协议、格式等完全透明。平行进入，无须排队！
λ3
3 Gbit/s
Input 3
Input 4
λ4
4 Gbit/s
Input 4
TDM
WDM
2006-8-25
8
通讯协议层（Layers of Standards）
Services
Voice Data Video Others
Adaptation
Voice Converter
IP Converter
• Ways to improve transmission capacity:
– Modulate light at higher and higher frequencies; – Sending multiple signals at different wavelengths through same fiber; (wavelength division multiplexing) – Adding more fibers
• 信号调制方式（即代表信息的数字或模拟信号怎样被运载？）
– 振幅调制（Amplitude Modulation）：几乎所有光纤通讯系统都使用AM，即传输光 强随信号强度同比变化。信号越强，则传输光也越强。由于通讯信号主流为数字信 号，那么经过振幅调制的数字信号就是一系列二进制“位”（bits）。 – 孤立子调制（Soliton Modulation）：自相关以抵制脉冲展宽效应。下一代技术。 – 频率调制（Frequency Modulation）：主要用于传送模拟信号。 – 相移调制（Phase-Shift Modulation）：针对光通讯与FM都处于研究实验室阶段。
Data Packaging for T3
Data Packaging for SONET
Data Packaging for FDDI for T3
IP Data Packaging for SONET
On-Fiber Standards
T3 (45Mbit/s Telephone Format)
Data Interface
IP Convertor
Video Interface
Converter
Interchange Formats
ATM Standard Interchange Format
Internet Protocol (IP) Exchange Format
Convert to Transmission Format
•
交换标准：
– ATM (asynchronous Transfer Mode): 数据包大小固定，53Bytes – Internet Protocol (IP): 数据包大小可变，数据头中包含数据大小和目的地信 息。
•
光纤传输标准：
– Digital Telephone Hierarchy: a sequence of TDM steps. – SONET/SDH (synchronous optical network, or synchronous digital hierarchy): developed for fiber-optic transmission of mixed traffic, including telephone calls and other signals. – Fiber Channel: intended for short-distance transmission in a computer system, network, building, or campus situation. – Gigabit Ethernet: intended for short-distance transmission on a LAN or as a backbone system linking networks on a campus. – Fiber Distributed Data Interface (FDDI): a networking standard established for transmitting 100Mbit/s.