2016-10-18

GPS Tracking Devices sensors usually record other

Records erroneously attributed to an animal because of inexact deployment information. This case is frequent and is usually due to an imprecise definition of the deployment time range of the sensor on the animal. A typical result is locations in the scientist’s office followed by a trajectory along the road to the point of capture. Records located outside the study area. In this case, coordinates are incorrect (probably due to malfunctioning of the GPS Phone Tracker sensor) and outliers appear very far from the other (valid) locations. This is a special case of impossible movements where the erroneous location is detected even with a simple visual exploration. This can be considered an extreme case of location bias, in terms of accuracy. Records located in impossible places. This might include (depending on species) sea, lakes or otherwise inaccessible places. Again, the error can be attributed to GPS sensor bias. Records that imply impossible movements (e.g. very long displacements, requiring movement at a speed impossible for the species). In this case, some assumptions on the movement model must be made (e.g. maximum speed). Records that imply improbable movements. In this case, although the movement is physically possible according to the threshold defined, the likelihood of the movement is so low that it raises serious doubts about its reliability. Once the location is tagged as suspicious, analysts can decide whether it should be considered in specific analyses.

Car GPS Tracker sensors usually record other ancillary information that can vary according to vendors and models. Detection of errors in the acquisition of these attributes is not treated here. Examples are the number of satellites used to estimate the position, the dilution of precision (DOP), the temperatures as measured by the sensor associated with the GPS and the altitude estimated by the GPS. Temperature is measured close to the body of the animal, while altitude is not measured on the geoid but as the distance from the centre of the earth: thus in both cases the measure is affected by large errors.

A source of uncertainty associated with Mini GPS Tracker data is the positioning error of the sensor. GPS error can be classified as bias (i.e. average distance between the ‘true location’ and the estimated location, where the average value represents the accuracy while the measure of dispersion of repeated measures represents the precision) and fix rate, or the proportion of expected fixes (i.e. those expected according to the schedule of positioning that is programmed on the GPS unit) compared to the number of fixes actually obtained. Both these types of errors are related to several factors, including tag brand, orientation, fix interval (e.g. cold/warm or hot start), and topography and canopy closure. Unfortunately, the relationship between animals and the latter two factors is the subject of a fundamental branch of spatial ecology: habitat selection studies. In extreme synthesis, habitat selection models establish a relationship between the habitat used by animals (estimated by acquired locations) versus available proportion of habitat (e.g. random locations throughout study area or home range). Therefore, a habitat-biased proportion of fixes due to instrumental error may hamper the inferential powers of habitat selection models. A series of solutions have been proposed. For a comprehensive review see Frair et al. Among others, a robust methodology is the use of spatial predictive models for the probability of GPS acquisition, usually based on dedicated local tests, the so-called Pfix. Data can then be weighted by the inverse of Pfix, so that positions taken in difficult-to-estimate locations are weighted more. In general, it is extremely important to account for GPS bias, especially in resource selection models

More information at http://www.jimilab.com/

2015-11-27

Diagnostic Monitoring Interface on Avago SFP Transceiver

WDM Optical Network

The present application note describes Avago’s SFP transceiver implementation of an enhanced digital diagnostic interface, compliant to the “Digital Diagnostic Monitoring Interface for Optical Transceivers” SFF-8472 Multi-Source Agreement (MSA.) The document also outlines the range of application options, both hardware and software, available to the host system for exploiting the digital diagnostic features of the transceiver. The enhanced digital interface allows real-time access to device operating parameters, and includes optional digital features such as soft control and monitoring of SFP I/O signals. In addition, it fully incorporates the functionality needed to implement digital alarms and warnings, as defined by the SFF-8472 MSA. With the digital diagnostic monitoring interface, the user has capability of performing component monitoring, fault isolation and failure prediction functions on their transceiver based applications.

AFBR-5715PZ with DMI

What is Diagnostic Monitoring Interface (DMI)?

As stated in the SFF-8472 MSA, the digital diagnostic monitoring interface (DMI) is an extension of the serial ID interface defined in the GBIC specification, as well as the SFP MSA. Both specifications define a 256-byte memory map in EEPROM that is accessible over a two-wire serial interface at the 8-bit address 1010000X (0xA0). The digital diagnostic monitoring interface makes use of the 8-bit address 1010001X (0xA2), so the originally defined serial ID memory map remains unchanged. The interface is backward compatible with both the GBIC specification and the SFP MSA.

What Can Digital Diagnostic Monitoring Interface Do?

Literally, DDM function can provide component monitoring on transceiver applications in details. However, DDM’s application is not limited to this. The SFF-8472 added DDM interface and outlined that DDM interface is an extension of the serial ID interface defined in GBIC specification, as well as the SFP MSA. DDM interface includes a system of alarm and warning flags which alert the host system when particular operating parameters are outside of a factory set normal operating. Thus, DDM interface can also enable the end user with the capabilities of fault isolation and failure prediction. This part is to illustrate what can be done with DDM.

Overview of applications of DMI

The digital diagnostic monitoring interface gives the host the ability to implement in-situ component monitoring on transceiver applications. Not only can the system user poll the individual parametric read-backs to monitor transceivers, the user can also take advantage of the DMI soft flags, and alarms and warnings to gauge link/transceiver health. Alarm flags signal impending link fault or significant functionality issues. Warning flags are meant to indicate potential compliance violations or non-ideal operating conditions. Soft Flags (bits on address 0xA2, byte 110) offer a mirror of the hard pin state warnings (e.g. TX fault, RX LOS) accessible via the two-wire serial interface.
The uses of the real-time parametric monitoring data can be broken down into the following functional categories with increasing complexity (either at the system software level or transceiver functional level):

Operating Environment Compliance Verification
The real-time diagnostic parameters can be monitored to alert the system when the transceiver’s specified operating limits are exceeded and compliance (to standard or datasheet) cannot be ensured. See section 3.2 for an example of implementation of alarms and warnings for compliance verification.
Fault Isolation
The diagnostic information can allow the host to pinpoint the location of a link problem and accelerate system servicing and minimize downtime.
Failure Prediction
The diagnostic information can allow the host system to identify potential link problems. Once identified, a “fail over” technique can be used to isolate and replace suspect devices before system uptime is impacted.

Providing parameter monitoring, fault isolation, and failure prediction, fiber optic transceivers with DDM help to ensure that the business can be proactive in preventative maintenance of the network and ensure business continuity. And it would easy to explain why modern transceivers are with DMI and why AFBR-5715PZ can replace AFBR-5710PZ (without DMI). It is irresistible development trend of industry and technology.

Article Source: http://www.sfp-transceiver-modules.com

2015-06-05

Brief Introduction of PON

WDM Optical Network

What is Passive Optical Networks

A PON is a fiber network that only uses fiber and passive components like splitters and combiners rather than active components like amplifiers, repeaters, or shaping circuits. Such networks cost significantly less than those using active components. The main disadvantage is a shorter range of coverage limited by signal strength. While an active optical network (AON) can cover a range to about 100 km (62 miles), a PON is typically limited to fiber cable runs of up to 20 km (12 miles). PONs also are called fiber to the home (FTTH) networks.

FTTx - Fiber to the x

The term FTTx is used to state how far a fiber run is. FTTx deployments cover varying amounts of that last distance.

FTTH for fiber to the home
FTTB for fiber to the building
FTTC for fiber to the curb or fiber to the cabinet
FTTN for fiber to the node or fiber to the neighbourhood
FTTP for fiber to the premises

In the basic method of operation for downstream distribution on one wavelength of light from OLT to ONU/ONT, all customers receive the same data. The ONU recognizes data targeted at each user. For the upstream from ONU to OLT, a time division multiplex (TDM) technique is used where each user is assigned a timeslot on a different wavelength of light. With this arrangement, the splitters act as power combiners. The upstream transmissions, called burst-mode operations, occur at random as a user needs to send data. The system assigns a slot as needed. Because the TDM method involves multiple users on a single transmission, the upstream data rate is always slower than the downstream rate.

PON is the acronym for Passive Optical Network is a point-to multipoint network. A PON consists of optical line terminal at the service provider’s central office and many number of optical network units near end users. The goal of PON is to reduce the amount of fiber.

There are two standards of PON:

GPON
EPON or GEPON

GPON (Gigabit PON) is the evolution of broadband PON (BPON) standard. The protocols used by GPON are ATM, GEM, and Ethernet. It supports higher rates and has more security. GPON uses optical wavelength division multiplexing (WDM) so a single fiber can be used for both downstream and upstream data. A laser on a wavelength (λ) of 1490 nm transmits downstream data. Upstream data transmits on a wavelength of 1310 nm. If TV is being distributed, a wavelength of 1550 nm is used.

EPON or GEPON (Ethernet PON) is the IEEE standard that uses Ethernet for sending data packets. Based on the Ethernet standard 802.3, EPON 802.3ah specifies a similar passive network with a range of up to 20 km. It uses WDM with the same optical frequencies as GPON and TDMA. The raw line data rate is 1.25 Gbits/s in both the downstream and upstream directions. You will sometimes hear the network referred to as Gigabit Ethernet PON or GEPON.

GPON ONT and EPON ONU Solution

Current and future demands for Internet access bandwidth have led to extensive deployment of FTTH technologies. Of these technologies, GPON and EPON provides the flexibility and cost advantages that service providers need to deliver services profitably to their subscribers. To support the increasing deployment of GPON and EPON in access networks worldwide, Fiberstore has developed full-featured ONT/ONU devices that can deliver a range of services. ONT is located at the customer premise, and ONU is located outside the home. EPON ONU can be working in different temperature and weather conditions. GPON ONT connects the PON to TV sets, telephones, computers, or a wireless router. More information about GPON ONT equipment please visit the fiberstore official website.

2015-05-28

CWDM PON Network construction and maintenance

The TDM-PON technology is not an effective solution to support over 100M bit rate FTTx access. DWDM PON could do that but it is not mature, probably not cost effective either. A Hybrid solution of CWDM-TDM-PON may be the best solution, and support up to 1x256 splitting ratio, while still offer up to 155M bit rate to premises sites.

Passive optical network (PON) is the vital solution to FTTx. It has three key elements: OLT (Optical Line Terminal), ODN (Optical Distributing Network) and ONU (Optical Network Unit). The ONUs of remote node, office or residence, share one OLT. The EPON ONU and EPON OLT are connected via ODN, which is passive.

The term PON (Passive Optical Network) emphasizes on the passive feature of the ODN. That passive structure offers low cost, and ease to maintenance to the FTTx provider. The popular TDM-PON solutions (GPON, GePON) use an optical power splitter to implement the passive ODNs. A popular implementation of this power splitter is based on PLC (Planar Light Circuit) technology. So, it is referred to as a PLC splitter, or a shorter jargon PLC. In fact, PLC has much wider applications than optical power splitter.

Once the TDM-PON (GPON, GePON) technology has reached its limitations, leading suppliers began to explore the next generation of PON infrastructure. The WDM-PON leverages the WDM (Wavelength Division Multiplex) technologies to implement the ODN. One of the decent designs is Nortel-LG (now LG-Ericsson) injection-locking approach (www.lgericsson.com).

Arguably, a switch to WDM-PON is inevitable, if network providers want to deliver higher bandwidth to the FTTx remote nodes. The GPON Fiber Access with 1x32 splitter configurations only deliver 300M bit rate to the premier site. To deliver the 1G bit rate to the remote note, one 10GPON can only support eight (8) remote notes. That is not cost effective.

So, the more pra ctical question is how to leverage the WDM feature of the ODN. Currently, the well discussed solution is a DWDM, pure WDM-PON. It has many benefits. However, the technology is not mature, leading to higher costs. Besides, it gives up the benefit of the existing TDM-PON solutions.

If we combine the mature, low cost CWDM and TDM-PON technologies together, we may have an affordable solution. The CWDM transceivers can support 2.5G bit rate with very competitive price. The 16-channel CWDM mux/demux module are cost effective. With 1x16 splitters, the CWDM-TDM ODN can support 1x256 splitting ratio, much higher than current 1x64 TDM-PON. With that splitting ratio, the premises sites can still have about 155M bit rate.

2015-05-27

EPON And GPON main difference - Used for downstream and upstream communications

Passive Optical Networks

The term FTTx is used to state how far a fiber run is. In FTTH, x is for home. You may also see it called FTTP or fiber to the premises. Another variation is FTTB for fiber to the building. These three versions define systems where the fiber runs all the way from the service provider to the customer. In other forms, the fiber is not run all the way to the customer. Instead, it is run to an interim node in the neighborhood. This is called FTTN for fiber to the node. Another variation is FTTC, or fiber to the curb. Here too the fiber does not run all the way to the home. FTTC and FTTN networks may use a customer’s unshielded twisted-pair (UTP) copper telephone line to extend the services at lower cost. For example, a fast ADSL line carries the fiber data to the customer’s devices.

The typical PON arrangement is a point to multi-point (P2MP) network where a central optical line terminal (OLT) at the service provider’s facility distributes TV or Internet service to as many as 16 to 128 customers per fiber line (see the figure). Optical splitters, passive optical devices that divide a single optical signal into multiple equal but lower-power signals, distribute the signals to users. An optical network unit (ONU) terminates the PON at the customer’s home. The ONU usually communicates with an optical network terminal (ONT), which may be a separate box that connects the PON to TV sets, telephones, computers, or a wireless router. The ONU/ONT may be one device.

GPON

Over the years, various PON standards have been developed. In the late 1990s, the International Telecommunications Union (ITU) created the APON standard, which used the Asynchronous Transfer Mode (ATM) for long-haul packet transmission. Since ATM is no longer used, a newer version was created called the broadband PON, or BPON. Designated as ITU-T G.983, this standard provided for 622 Mbits/s downstream and 155 Mbits/s upstream.

While BPON may still be used in some systems, most current networks use GPON, or Gigabit PON. The ITU-T standard is G.984. It delivers 2.488 Gbits/s downstream and 1.244 Gbits/s upstream.

GPON uses optical wavelength division multiplexing (WDM) so a single fiber can be used for both downstream and upstream data. A laser on a wavelength (λ) of 1490 nm transmits downstream data. Upstream data transmits on a wavelength of 1310 nm. If TV is being distributed, a wavelength of 1550 nm is used.

While each GPON ONT gets the full downstream rate of 2.488 Gbits/s, GPON uses a time division multiple access (TDMA) format to allocate a specific timeslot to each user. This divides the bandwidth so each user gets a fraction such as 100 Mbits/s depending upon how the service provider allocates it.

The upstream rate is less than the maximum because it is shared with other ONUs in a TDMA scheme. The GPON OLT determines the distance and time delay of each subscriber. Then software provides a way to allot timeslots to upstream data for each user.

The typical split of a single fiber is 1:32 or 1:64. That means each fiber can serve up to 32 or 64 subscribers. Split ratios up to 1:128 are possible in some systems.

As for data format, the GPON packets can handle ATM packets directly. Recall that ATM packages everything in 53-byte packets with 48 for data and 5 for overhead. GPON also uses a generic encapsulation method to carry other protocols. It can encapsulate Ethernet, IP, TCP, UDP, T1/E1, video, VoIP, or other protocols as called for by the data transmission. Minimum packet size is 53 bytes, and the maximum is 1518. AES encryption is used downstream only.

The latest version of GPON is a 10-Gigabit version called XGPON, or 10G-PON. As the demand for video and over the top (OTT) TV services has increased, there is an increasing need to boost line rates to handle the massive data of high-definition video. XGPON serves this purpose. The ITU standard is G.987.

XGPON’s maximum rate is 10 Gbits/s (9.95328) downstream and 2.5 Gbits/s (2.48832) upstream. Different WDM wavelengths are used, 1577 nm downstream and 1270 nm upstream. This allows 10-Gbit/s service to coexist on the same fiber with standard GPON. Optical split is 1:128, and data formatting is the same as GPON. Maximum range is still 20 km. XGPON is not yet widely implemented but provides an excellent upgrade path for service providers and customers.

EPON

The Institute of Electrical and Electronic Engineers (IEEE) developed another newer PON standard. Based on the Ethernet standard 802.3, EPON 802.3ah specifies a similar passive network with a range of up to 20 km. It uses WDM with the same optical frequencies as EPON ONU. The raw line data rate is 1.25 Gbits/s in both the downstream and upstream directions. You will sometimes hear the network referred to as Gigabit Ethernet PON or GEPON.

EPON is fully compatible with other Ethernet standards, so no conversion or encapsulation is necessary when connecting to Ethernet-based networks on either end. The same Ethernet frame is used with a payload of up to 1518 bytes. EPON OLT does not use the CSMA/CD access method used in other versions of Ethernet. Since Ethernet is the primary networking technology used in local-area networks (LANs) and now in metro-area networks (MANs), no protocol conversion is needed.

There is also a 10-Gbit/s Ethernet version designated 802.3av. The actual line rate is 10.3125 Gbits/s. The primary mode is 10 Gbits/s upstream as well as downstream. A variation uses 10 Gbits/s downstream and 1 Gbit/s upstream. The 10-Gbit/s versions use different optical wavelengths on the fiber, 1575 to 1580 nm downstream and 1260 to 1280 nm upstream so the 10-Gbit/s system can be wavelength multiplexed on the same fiber as a standard 1-Gbit/s system.

Summary

Telecommunications companies use PONs to provide triple-play services including TV, VoIP phone, and Internet service to subscribers. The benefit is much higher data rates that are essential to video distribution and other Internet services. The low cost of passive components means simpler systems with fewer components that fail or require maintenance. The primary disadvantage is the shorter range possible, commonly no more than 20 km or 12 miles. PONs are growing in popularity as the demand for faster Internet service and more video grows. GPON is the most popular in the U.S., such as Verizon’s Foist system. EPON systems are more prevalent in Asia and Europe.

2015-05-26

Fiber structure - advantages and disadvantages

The socio-economic benefits of fiber are beyond question. Fiber to the Premise (FTTP) can boost economic development, spark innovation and improve the way people live and work.

For network operators looking to deploy FTTP there are multiple factors that need to be taken into account when planning an installation. These include:

Topography
Regulation
Technical choices
Implementation cost
The need to future-proof investment

Every deployment is different. Therefore to help network operators make the right choices for their implementation we’ve created the Complete Guide to Fiber to the Premises Deployment eBook. Which is available as a free download here. Over the next few months we’ll summarise some of the key points of the guide in a series of blog posts, beginning with fiber architectures.

Passive Optical Networking

In a Passive Optical Networking architecture the operator deploys an Optical Line Terminal (OLT) in the Point of Presence (POP) or central office. One fiber runs to the passive optical splitter and a fan-out connects a maximum of 64 end users with each having an Optical Networking Unit (ONU) at the point where the fiber terminates.

Point to Point Architecture

In contrast, a Point to Point (P2P) architecture is more complex. It has a core switch at the central office, which connects over optical fiber cables to an aggregation switch at the distribution point, typically located at a street corner. These aggregation switches have many fiber ports and each port directly connects to an Optical Network Termination (ONT), which is located inside or outside the customer’s residence or business premises.

Each option has its own strengths and weaknesses:

Positives (PON):

A PON infrastructure is much less expensive to implement and maintain than PON.
The fiber splitters at the centre of a PON infrastructure don’t require any power supply.
Faster to deploy than a more complex PON infrastructure.

Negatives (PON):

PON infrastructures offer a limited level of bandwidth as it is shared between multiple subscribers.
Bandwidth is asymmetric, with much greater download capacity compared to upload.
Once implemented a EPON network is more difficult to update, particularly if bandwidth requirements change.
As optical splitters have both bandwidth limitations (particularly upstream).

2015-05-25

How much you know about the classification of the optical fiber module？

Fiber optical module is characterized by three sets of performance criteria: transceiver, receiver, and transmitter. The transmitter converts electrical signals into
light signals, through the fiber optical transmission, the receiving end of the optical signals are converted into electric signals.

According to the optical module function, fiber optic transceivers can be divided into fiber optical receiver module, fiber optical transmission module, fiber optical
transceiver module and fiber optical transponder module.

Fiber optic transceiver module main function is to achieve the conversion between optical-electrical and electrical-optical, including optical power control,
modulation transmission, signal detection, IV conversion and limiting amplifier decision regeneration, in addition, there are security information query, TX-disable
and other functions. Common fiber optic transceiver modules are: SFP, SFF, SFP+, GBIC, XFP and so on.

Fiber optical transmission module not only has photoelectric conversion function, but also it integrates a lot of signal processing functions, such as: MUX / DEMUX,
CDR, function control, energy acquisition and monitoring. Common fiber optical transmission modules: 200/300pin, XENPAK, and X2/XPAK so on.

The optical transceiver module, referred to as optical module or fiber optic module, is an important device in fiber optical communication system.

According to the main parameters of fiber optical module.

Pluggable: hot pluggable and non-hot pluggable;

Package: SFP, GBIC, XFP, Xenpak, X2, 1X9, SFF, 200/3000pin, XPAK.

Transmission Rate: Transmission rate refers to the number of gigabits transmitted per second, per unit of Mb/s or Gb/s. Optical modules cover the following main rate:
low rates, Fast, Gigabit, 2.5G, 4.25G, 4.9G, 6G, 8G, 10G and 40G.

According to the optical module package.

1.XFP (10 Gigabit Small Form Factor Pluggable) is a hot pluggable transceiver, is independent communication protocol optical transceiver for 10G bps Ethernet, SONET /
SDH and Fiber Channel.

2. SFP transceivers (small form factor pluggable), currently are the most widely used.

3.GigacBiDi series of single-mode bidirectional optical module, uses WDM technology, achieving a fiber optic transmits two-way information (point to point
transmission, especially for fiber optic resources are insufficient, need a fiber bi-directional signal transmission). GigacBiDi series include SFP Bidirectional
(BiDi), GBIC Bidirectional (BiDi), SFP+ Bidirectional (BiDi), XFP Bidirectional (BiDi), SFF Bidirectional (BiDi) and so on.

4.RJ45 transceiver is electrical port small form factor pluggable module, also known as the power module or electrical interface module.

5.SFF According to their pin, SFF transceivers are divided into 2×5, 2×10, etc.

6 Gigabit Ethernet Interface Converter (GBIC) module.

7 Passive Optical Network PON (GPON ONT, GPON OLT, EPON OLT, EPON ONU) optical module.

8.40Gbs high-speed optical modules.

9.SDH transmission module (OC3, OC12, OC48).

10 Storage modules, such as 4G, 8G, etc.