Application of fiber optic connectors and terminals

Fiber optic connectors and A/V industry BNC connector commonly used by different, with fiber optic technology continues to mature and get progressive development. Effect of copper connector signal loss of AV systems are generally not large, but the optical connection is different, its transmission system in each interface will play a very big influence. Let's look at the physical fiber optic connection problems arising from optical fiber transmission equipment itself may direct connection, but in some cases, most or almost all connectivity options are all man-made fiber transmission personally. Semaphore fiber optic cable in the signal transmission process of the loss is mainly determined by the quality and type of use of fiber optic cables, each connecting terminal will have some signal loss. Depending on the type of fiber optic connector selected by the user, the connection end signal is lost a combined total may exceed the amount of signal loss of the fiber optic cable itself.

Maintain a normal operation

In the optical fiber system design, system to normal operation, it reached very good results, in the system design, we need to consider the system may occur some unexpected problems, and let the system has reached normal operating results. In the system design, we have to consider the worst system possible situation and plan accordingly, expecting better operating results. Fiber Optic Connector designer must keep in mind to this idea. In system design, security, stability, system connection requires smooth fiber ends, Founder. The connection between the client and the client must be accurate and correct, or even to achieve micron precision, millionths of a meter. Commonly used diameter multimode fiber from 50-62.5 microns and single-mode fiber is only 8-9 microns in diameter. This compared to the diameter of a human hair in diameter (17-180 microns), showing no trace of error can bring in catastrophic losses.

Precision optical fiber connection to the equipment requirements are very strict, so connector must be very clean. Fiber optic connectors and accessories are usually mounted on a set of house, a finger print or external dust might seriously affect connector performance, even lead to transmission failure, therefore, when the connector is not connected, it should be kept in clean protective cover in.

In connection, we should also be fiber optic connector wedge tight, in the present all the fiber optic connector design, through the "collar" to ensure accurate at the time with the connector. Viscose fiber terminals or by crimping the ferrule inside the confining, as a permanent member. After inserting a built-in optical fiber, put the smooth ferrule end mill for fiber optic connectors provide a smooth interface. Rings are usually made of relatively hard material such as ceramics, of course, it may be stainless steel, plastic or tungsten carbide material, SC, ST and FC common ferrule diameter 2.5 mm, LC universal ferrule diameter 1.25 mm. Since the feature rings can be produced in accordance with the requirements of precision, it will become the primary fiber optic connector to determine important characteristics. Among the many connections ferrule, the spring-loaded ferrule ensures the container is connected coaxially aligned between the optical fiber and LED or laser source.

With the expansion of technology development and application of fiber optic connectors are also developing rapidly. Fiber optic connectors used now on the market there are about 12 kinds and even more, each of which is to meet the specific needs and came into being, of course, there are some technical limitations. Now the market trend is mainly towards the moderate price, compact connector model development to support greater transmission density of new transmission distribution system requirements. As user expectations, as the continuous development of the telecommunications industry also contributed to the large-scale application of optical fibers is due to various types of communication and entertainment services on fiber-optic connections due to the rapid growth in demand largely.

Consider terminal

Traditionally, fiber optic terminal is generally slower, the price is higher, the equipment requirements and technical requirements are high. When considering a single-mode fiber optic cable in the terminal, you should take into account several factors in this regard. In some cases, we can choose some already set in accordance with various fiber types good terminal cables.

Tailor-mount applications, we can select a specific terminal, however, adopted after splicing tools, you can reduce on-site terminal extension of the length of the single-mode fiber, reducing the use of the equipment and technology of the quantity demanded. After the multimode fiber optic cable, the new splicing method using a simple optical fiber cutting method, will be assembled into a pre-designed cable connector / cable. This method is very simple, but the fiber-to-fiber connectors butt joints usually uses a special optical gel, so that fiber optic terminal curdle.

WTD develop high-speed polarization multiplexing coherent detection optical module technology considerations

In order to achieve accurate, effective, and reliable coherent optical communication, WTD in the coherent optical communication technology to develop high-speed polarization multiplexing coherent detection optical module products mainly consider the following several technical points.

1. Using high-standard light source technology

Coherent optical fiber communication system for signal light and local oscillator light source is relatively high, it requires a narrow spectral lines, high frequency stability. Linewidth light source itself determines the system can achieve the lowest error rate, should be minimized, while the frequency of the semiconductor laser to change the operating temperature and injection current is very sensitive to the variation amount is generally in the tens of gigahertz per degree Celsius and the tens of gigahertz per mA, therefore, for the frequency stability, in addition to the injection current and temperature stability, we must also take other frequency stabilization measures to maintain a stable optical frequency.

2. To achieve a breakthrough in terms of access technology

Coherent detection receiver technology consists of two parts, one is the light receiver technology, the other is a variety of standard intermediate frequency after demodulation techniques.

Balanced receiver method: frequency shift keying (FSK) standard, since the semiconductor laser modulation process will inevitably with additional amplitude modulation noise, using a balanced approach reduces AM reception noise. The main idea of ​​balancing law when the optical signal from the optical fiber into the local oscillator light by polarization control to ensure that the polarization state of the signal to adapt the local oscillator and signal lights through the polarizing beam splitter into two paths, and receives two identical PIN photodetector, such that the output of the two photodetectors is equal amplitude and inverted envelope signal, then the two signals after synthesis, so that doubling the FM signal, the AM noise and spurious cancel each other The DC component also counteract, to eliminate the influence of noise amplitude modulation requirements.

Polarization control technology: coherent optical communication system receiver must request signal light and the LO light polarized with biased in order to achieve good mixing effect and improve reception quality. Signal light after the single-mode fiber for long distance transmission, the polarization is random fluctuation, in order to solve this problem, a lot of ways, such as using polarization maintaining fiber, polarization controller and polarization diversity reception and other methods. When the light transmission in the general fiber, phase and polarization plane will randomly change the polarization maintaining fiber it is through the selection process and material makes the light phase and polarization unchanged specialty optical fiber, but the fiber loss, the price is very expensive; polarization The controller is mainly the signal light and the LO light with bias, this method is relatively slow response speed, loop control requirements are relatively high; polarization diversity receiver is the use of signal light and the LO light After mixing, the polarization The mixed light beam components into two mutually perpendicular polarization components, the LO light in two perpendicular polarization components by the polarization controller, so that the two components of equal power, so that when the signal light of random polarization fluctuations may cause one of the intermediate frequency signal branch decline, but another branch of the IF signal still exists, so the demodulated signal of the system and the resulting polarization of the signal light is almost independent of the technical response faster, more practical, but to achieve more complex.

3. The use of external optical modulation technology

Because when a parameter of the semiconductor laser direct modulation of the optical carrier, always incidental to other parasitic oscillation parameters, such as amplitude shift keying (ASK) modulation directly associated with the phase change, and the modulation depth will be limited. In addition, the frequency characteristics will encounter uneven and relaxation oscillation problems. Thus, in the coherent optical communication system, in addition to direct injection current can FSK frequency modulation, the other is the use of external light modulation.

4. The rational use of non-linear crosstalk control technology

Since the coherent optical communication, often using DWDM technology. Thus, the optical fiber nonlinear effects may make a coherent optical communication channel signal strength and phase affected by other channel signals to form non-linear crosstalk.

Infineon RPR chip solution

Infineon of FreaTM PoS Framer / RPR MAC IC is the industry's first draft protocol IEEE 802.17 RPR (Resilient Packet Ring) version 2.1-compliant 10G RPR chip, which is the Infineon existing optical networking solutions the latest addition.

Infineon said the product integrates the previous IC requires a minimum of four to complete the function, with a high degree of integration, thus greatly reducing the cost of user equipment, power consumption, size, and complexity of the software and hardware design.

RPR technology support high-speed optical network system Ethernet communication, the launch of the Infineon chip can complete PoS (Packet-over-SONET) into frame unit, RPR MAC (Media Access Control) and XAUI SerDes (serializer / deserializer string) function, which are necessary for the deployment of RPR in the metro and wide area networks. At the same time, the chip built-in 1MB of memory, support for 16-bit 800MHz SPI-4.2 and 4 3.125GHz XAUI interface, so when configuring RPR, no need for external SerDes products can connect two chips together.

Optical Communication Systems technology trends - beyond 100G

With the progress of social information process, to video, cloud computing, networking and the representative of the emerging business demand for bandwidth surge, the existing backbone optical transmission system interconnection capacity can not meet the growing demand, an urgent requirement to further enhance transmission capacity.

In fact, as experienced from 2.5Gbit/s-> 10Gbit/s-> 40Gbit/s-> 100Gbit/s transmission capacity to enhance network surge in demand, its single channel optical transmission system transmission rate, is preparing the next generation Ultra 100G optical transmission systems. The optical transmission multiplexing dimension from a simple time division multiplex development, wavelength, frequency, polarization, multidimensional multiplex transmission mode, multi-pronged approach. Future demand for network capacity optical transmission, Pbit multi-core space division multiplexing as well as orbital angular momentum of photons reuse industry has become a hot topic. In the specific implementation, advanced quadrature amplitude modulation, coherent reception, digital signal processing, multi-carrier technology and optoelectronic integrated technology and other new technologies have been gradually introduced and continue to optimize and improve the optical transmission performance and reduce the cost of optical transmission.

Consider cost and compatibility, etc., based on full use of the fiber optic cable has been laid, the existing optical transmission systems by upgrading and transformation of the optical transceiver unit to raise a single wavelength channel transmission data rate of ways to enhance system capacity, it has the best cost and feasibility. Ultra 100G optical transmission will inherit design 100G optical transmission systems, the use of polarization multiplexing, multi-level modulation spectrum efficiency, increase the use of digital coherent reception receiver sensitivity and channel equalization capability.

Ultra 100G optical transmission is intended to further enhance the transmission capacity in a single fiber band resources available under the same circumstances, the key is to improve the efficiency of spectrum utilization and spectrum resources. For optical transmission systems, narrowband filtering effect of fiber loss caused by the window limits the available bandwidth of optical devices and optical transmission path caused by cascade claim maximize spectrum efficiency light transmission; non-linear effect of the optical transmission path optical transmission power requirement maximize efficiency. In addition, the level of light transmission symbol photovoltaic device baseband bandwidth also restricted.

In response to these super-100G optical transmission challenges, solve industry from the following aspects: ① full use of the optical signal can be modulated dimension (amplitude, phase, polarization) to carry data to improve spectral efficiency; ② multi-carrier orthogonal frequency division multiplexing technology to improve spectrum utilization and reduce the transmission rate to suppress symbol dispersion effect, reduce light, electrical parts bandwidth requirements; ③ using digital coherent receiver technology to improve the sensitivity and channel equalization capability of the receiver, using higher gain The error correction coding to improve the robustness of the system. ④ use of advanced optical integration technology to reduce size, lower power consumption and increase system reliability.

It should be noted that, despite the multi-dimensional multi-level modulation can improve spectral efficiency, to reduce the transmission channel and the photovoltaic device bandwidth requirements, but the minimum spacing will reduce the multilevel modulation symbol constellation between sensitivity and lower OSNR transmission damage tolerance capability. Therefore, the selection of higher-level QAM modulation may improve spectral efficiency and transmission rate over 100G, but since the strength of noise and phase noise tolerance diminished capacity, the transmission distance may be much lower than the current system 100G.

Optoelectronic devices integration technology is the basis for ultra-100G optical transmission to achieve. Although the multi-carrier transmission stages can reduce the bandwidth requirements of optical systems, electrical parts, the device power consumption is reduced by the square of the linear growth increase, but the bandwidth and power requirements are still alarming. Optoelectronic devices integrated technology is a key factor Ultra 100G optical transmission design feasibility and system performance.

Given the current business needs and optoelectronic devices technology level, 400Gbit/s optical transmission rate is the most feasible and cost-effective solution. Gemini carrier based on a flexible grid polarization multiplexing 16 quadrature amplitude modulation (2SC-PM-16-QAM) a 400G optical transmission is generally optimistic about the industry one of the options. The program for each transmission channel occupies 75GHz bandwidth and spectral efficiency can reach 5.3bit/s/Hz, compared with 100Gbit/s optical transmission 2bit/s/Hz spectral efficiency can be greatly improved. As a result of more intensive 16QAM modulation, 400G transmission damage tolerance capability (transmission distance) declined compared with 100G optical transmission system, expected to be the first application in the metro and data center interconnect applications.