Self-characterization tunable optical network unit

A tunable optical transmitter, comprising a tunable laser comprising a distributed Bragg reflector (DBR) section, a phase section, and a gain section, a photodiode detector (PD) optically coupled to the tunable laser, wherein the tunable optical transmitter lacks a temperature controller, and wherein the tunable optical transmitter is configured to lock onto a wavelength at different operating temperatures.

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

A passive optical network (PON) is a point-to-multipoint, fiber to the premises network architecture in which unpowered optical splitters are used to enable a single optical transmitter to serve multiple premises. A PON may consist of an optical line terminal (OLT) at the service provider's central office and a number of optical network units (ONUs) near end users. A PON reduces the amount of fiber and central office equipment required compared with point-to-point architectures. A number of ONUs may share the same wavelength over the optical fiber.

SUMMARY

In one embodiment, the disclosure includes a tunable optical transmitter, comprising a tunable laser comprising a distributed Bragg reflector (DBR) section, a phase section, and a gain section, a photodiode detector (PD) optically coupled to the tunable laser, wherein the tunable optical transmitter lacks a temperature controller, and wherein the tunable optical transmitter is configured to lock onto a wavelength at different operating temperatures.

In another embodiment, the disclosure includes a tunable optical transmitter, comprising a tunable laser comprising a distributed Bragg reflector (DBR) section, a phase section, and a gain section, a DBR section current generator coupled to the DBR section, a phase section current generator coupled to the phase section, wherein the phase section current generator is optically combined with the DBR section current generator, a gain bias generator coupled to the gain section and configured to bias the gain at a current exceeding a threshold current for the gain section, a power monitor coupled to the tunable laser and configured to measure an output laser power for a plurality of scanning current values, and a processor coupled to the power monitor and configured to determine a first current value for a power maximum point and a second current value for a power minimum point of the output laser power, and determine a DBR bias current value, a phase section bias current value, and a gain bias current value for a substantially maximal power output for a wavelength.

In another embodiment, the disclosure includes a method for automatic self-characterization of a tunable optical network unit (ONU), comprising applying a first bias to a gain section of a tunable laser, wherein the first bias exceeds a threshold current for the gain section, applying a second bias to one of a phase section and a DBR section of the tunable laser, applying a scanning current to one of the DBR section and the phase section, measuring a laser output power curve for the scanning current, determining a power maximum current value and a power minimum current value from the laser output power curve for the tunable laser, and transmitting a data signal based on the determined power maximum current value and the power minimum current value.

DETAILED DESCRIPTION

Disclosed herein are systems, methods, and apparatuses for a self-characterization tunable ONU. In an embodiment, the tunable transmit optical sub-assembly (TOSA) of a tunable ONU is characterized by means of tunable laser output power characterization (undulation—e.g., power fluctuations) with the wavelength tuning (e.g., by tuning the distributed Bragg reflector (DBR) and the phase bias current). As an initial or recurrent configuration, a scanning voltage or current may be applied to the DBR section of the tunable laser, and the photodiode detector (PD) power monitor of the tunable laser may record the tunable laser's output power value. The data of laser output power and the power's correspondence scanning current value may be saved to the ONU memory. The Microcontroller or field-programmable gate array (FPGA) of the ONU may analyze the data and find the DBR section and/or laser phase section current values for which the laser output power has maximum and minimum values. These values may be related to laser mode hopping and optimal working points depending on whether the PD power monitor is on the gain side or on the DBR side. The method of obtaining the optimal working points on the laser phase section may be similar to the DBR section scanning approach. In an embodiment, scanning voltage or current on the laser phase section may also be performed. These current values of the phase bias points may also be saved to the ONU memory and used for ONU wavelength set-up in the system.

During ONU operation, the saved values may be used to re-characterize the tunable ONU transmitter's wavelength, which may have wandered due to environmental (e.g., temperature) changes. The DBR mode hopping bias current data, the phase mode hopping bias current data, and the DBR optimal bias point values may be used for new DBR scanning current values for the tunable transmitter wavelength setting. Furthermore, these values may be used to re-characterize the tunable ONU transmitter to ensure substantially maximum power output for a particular channel or wavelength (which increases transmission distance) since the wavelength may be quasi-stable for a given range of bias currents, but the output power may vary greatly for the same wavelength. The tunable ONU transmitter may re-characterize itself once a day to several times a day without interrupting data transmission. In an embodiment, the disclosed tunable self-characterization transmitter may be used as a second phase Next Generation PON (NGPON2) (40 gigabit PON (GPON) or 80 GPON) ONU transmitter. The disclosed self-characterizing tunable transmitter may save tunable TOSA characterization cost and may make a PON system more flexible and manageable. Although described with respect to an ONU, the systems and methods described herein may also be used in an OLT or other optical transmitter.

FIG. 1illustrates one embodiment of a PON100. The PON100comprises an OLT110, a plurality of ONUs120, and an optical distribution network (ODN)130, which may be coupled to the OLT110and the ONUs120. The PON100may be a communications network that does not require any active components to distribute data between the OLT110and the ONUs120. Instead, the PON100may use the passive optical components in the ODN130to distribute data between the OLT110and the ONUs120. In an embodiment, the PON100may be a Next Generation Access (NGA) system, such as a ten gigabit per second (Gbps) GPON (XGPON), which may have a downstream bandwidth of about ten Gbps and an upstream bandwidth of at least about 2.5 Gbps. Alternatively, the PON100may be any Ethernet based network, such as an Ethernet PON (EPON) defined by the Institute of Electrical and Electronics Engineers (IEEE) 802.3ah standard, a 10 Gigabit EPON as defined by the IEEE 802.3av standard, an asynchronous transfer mode PON (APON), a broadband PON (BPON) defined by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) G.983 standard, a GPON defined by the ITU-T G.984 standard, or a wavelength division multiplexed (WDM) PON (WPON), all of which are incorporated herein by reference as if reproduced in their entirety.

In an embodiment, the OLT110may be any device that is configured to communicate with the ONUs120and another network (not shown). Specifically, the OLT110may act as an intermediary between the other network and the ONUs120. For instance, the OLT110may forward data received from the network to the ONUs120, and forward data received from the ONUs120onto the other network. Although the specific configuration of the OLT110may vary depending on the type of PON100, in an embodiment, the OLT110may comprise a transmitter and a receiver. When the other network is using a network protocol, such as Ethernet or Synchronous Optical Networking/Synchronous Digital Hierarchy (SONET/SDH), that is different from the PON protocol used in the PON100, the OLT110may comprise a converter that converts the network protocol into the PON protocol. The OLT110converter may also convert the PON protocol into the network protocol. The OLT110may be typically located at a central location, such as a central office, but may be located at other locations as well.

In an embodiment, the ONUs120may be any devices that are configured to communicate with the OLT110and a customer or user (not shown). Specifically, the ONUs120may act as an intermediary between the OLT110and the customer. For instance, the ONUs120may forward data received from the OLT110to the customer, and forward data received from the customer onto the OLT110. Although the specific configuration of the ONUs120may vary depending on the type of PON100, in an embodiment, the ONUs120may comprise an optical transmitter configured to send optical signals to the OLT110and an optical receiver configured to receive optical signals from the OLT110. Additionally, the ONUs120may comprise a converter that converts the optical signal into electrical signals for the customer, such as signals in the Ethernet or asynchronous transfer mode (ATM) protocol, and a second transmitter and/or receiver that may send and/or receive the electrical signals to a customer device. In some embodiments, ONUs120and optical network terminals (ONTs) are similar, and thus the terms are used interchangeably herein. The ONUs120may be typically located at distributed locations, such as the customer premises, but may be located at other locations as well.

In an embodiment, the ODN130may be a data distribution system, which may comprise optical fiber cables, couplers, splitters, distributors, and/or other equipment. In an embodiment, the optical fiber cables, couplers, splitters, distributors, and/or other equipment may be passive optical components. Specifically, the optical fiber cables, couplers, splitters, distributors, and/or other equipment may be components that do not require any power to distribute data signals between the OLT110and the ONUs120. Alternatively, the ODN130may comprise one or a plurality of active components, such as optical amplifiers. The ODN130may typically extend from the OLT110to the ONUs120in a branching configuration as shown inFIG. 1, but may be alternatively configured in any other point-to-multi-point configuration.

The PON100may have a maximum transmission distance less than or equal to about 20 kilometers (km) and a splitting ratio less than or equal to about 1:64. For instance, a plurality of splitters may be used in the ODN130to split each branch of fiber into a plurality of branches until reaching such splitting ratio. Typically, to increase the splitting ratio and increase the maximum transmission distance of the PON100, a plurality of optical amplifiers and/or regenerators may be added, for instance to couple some of the fiber cables in the ODN130and thus boost the optical signal power for longer reach and/or larger splitting ratio. However, such combination of splitters and optical amplifiers (or regenerators) may increase the cost of deployment, which may not be desirable or practical.

In an embodiment, a 40 Gigabit per second (Gb/s) PON system with four wavelengths (10 Gb/s per wavelength) are used for downstream data transmission (e.g., from the OLT to the ONUs), and four wavelengths (2.5 Gb/s or 10 Gb/s (with electroabsorption (EA) modulator) per wavelength) are used for upstream data transmission (e.g., from the ONUs to the OLT). In order to decrease ONU wavelength inventory, a three-section tunable laser disclosed herein may be used at the ONU transmitter. The disclosed three-section tunable laser self-characterization approach may lower tunable ONU cost and/or complexity and 40 Gb/s (40 G) PON system cost and/or complexity.

FIG. 2is a schematic diagram of a self-characterization tunable ONU transmitter (Tx)200in accordance with a disclosed embodiment. The ONU Tx200may comprise a memory and processing unit204, a DBR and phase scanning and bias current generator202, a gain bias and radio frequency (RF) generator206, a submount214comprising a PD228and a tunable laser220, a splitter216, a PD power monitor210, an isolator208, a heat sink218, an optical waveguide (or optical fiber)212, and an optional thermoelectric cooler (TEC) temperature controller (not shown). The tunable laser220may comprise a DBR section222, a phase section224, and a gain section226. The submount214, splitter216, PD power monitor210, isolator208, and optical fiber212may be mounted on heat sink218. In an embodiment that includes a TEC temperature controller, the TEC temperature controller may control the temperature of the tunable laser220within a specified frequency range.

The memory and processing unit204may comprise a memory and a processor. The processor in memory and processor unit204may be a single-core or multi-core microcontroller, a CPU, or a FPGA. The memory and processor unit204may be used to measure, correlate, and store the various values (e.g., current versus wavelength) discussed herein. The PD228may be used for detecting optical signals and/or automatic characterization of the tunable laser220. The DBR and phase scanning and bias current generator202may be coupled to DBR section222and phase section224and may provide a bias voltage/current to the DBR section222and the phase section224during both the configuration (e.g., DBR/phase scanning) and data transmission. The gain bias and RF generator206may be coupled to gain section226and used to bias the gain section226of the tunable laser220during both configuration (e.g., DBR/phase scanning) and data transmission. Heat sink218may remove heat from the submount214, the splitter216, the PD power monitor210, the isolator208, and/or the optical fiber212.

The PD power monitor210may determine the output laser optical power from one face of the splitter216. Depending on the splitting ratio, the optical power detected by the PD power monitor210may be between about 2% and about 10% of the total output optical laser power. Isolator208allows the transmission of optical signals in only one direction (e.g., from the laser220to optical fiber212). Isolator208prevents unwanted feedback into the laser220. Optical fiber212provides a medium to transmit the optical signal(s) from the laser220to an ODN.

The laser220may be excited or lase via current/voltage applied to the gain section226. In an embodiment, two current sources may be used for current generator202. One current source may be for the DBR, and the other current source may be for the phase. The two current sources may be different and may provide a constant current bias and a scanning current profile for the DBR section222and the phase section224of the laser220, respectively. At the back side of the laser220, a PD228may be used to determine the laser wavelength and/or characterize the tunable laser220wavelength tuning specifications, such as how many mode hopping the laser220has for a specific DBR current tuning range and the current value at mode hopping points. Similar results may be obtained from phase section224current scanning. The laser power from the laser's gain226facet output (e.g., the front side of the laser220) may be coupled into an input on the optical splitter216. The optical splitter216may have two output facets. One output facet may be coupled to the optical fiber212via isolator208, and the other output facet may be coupled to the PD power monitor210. The splitter splitting ratio of optical power to optical fiber212and to optical power PD210may be in the range of about 98:2 to about 90:10. Thus, most of the power may be directed into the optical fiber212(e.g., between about 90% and about 98% of the power) and about 2% to about 10% of optical power is provided to the PD power monitor210.

FIG. 3is a DBR scanning current profile300for the self-characterization tunable ONU300shown inFIG. 2. The current profile300shows the DBR current in milliamps (mA) as a function of scanning time. As shown, the DBR current has a linear relationship with time with the current increasing linearly from zero with increasing time. In an embodiment, the DBR scanning current may be a constant range steps or various range steps and the step range may be between about 0.01 mA to about 0.1 mA or other steps.

FIG. 4is a graph of the phase section scanning current profile400for the self-characterization tunable ONU Tx200shown inFIG. 2. The phase section scanning current profile400is similar to the DBR current profile300. The phase section scanning current profile400shows the phase current in mA as a function of scanning time. The phase current increases linearly from about zero mA with increasing time as shown. In an embodiment, the phase scanning current step is uniform and the current step size may be from about 0.005 mA to about 0.01 mA. Other values for the current step size may be used in other embodiments.

Returning toFIG. 2, when the tunable laser220gain section226is biased at its threshold current above, for example, two times threshold current, the laser220lases. When (1) a scanning current is applied on the DBR section222and (2) the gain section226and the phase section224bias currents are kept constant, the laser220output power undulates.FIG. 5shows output power undulation curve with DBR section222current change, which is measured from the DBR section222facet and DBR spontaneous emitting light power is ignored. Alternatively, an edge filter (not shown) may be used to remove DBR spontaneous emitting light. The phase section224may be biased at a certain current value which may be in the phase scanning current range or the phase bias current may be zero.

FIG. 5is a graph500of DBR facet output power versus DBR current for the self-characterization tunable ONU Tx200shown inFIG. 2. Graph500shows the relationship of the tunable laser output power from the DBR facet with the DBR bias current. The graph500shows that the DBR facet output power generally decreases with increasing DBR current with localized maximums and minimums in the DBR facet output power occurring at various points as the DBR current is increased. The maximum points are the laser mode hopping positions. These data points may be saved in the memory of memory and processing unit204. The memory and processing unit204may find the current values that correspond to these maximum power points and save them to the memory of memory and processing unit204. The average of two adjacent maximum point current values may be the substantially optimal DBR bias current value at that mode. For the results shown inFIG. 5, the laser was biased at two times the threshold current, and the phase bias current was zero.

FIG. 6shows the curve600of laser output power from the DBR section222facet and the phase section224bias current for the self-characterization tunable ONU Tx200shown inFIG. 2. For the phase section224, the results of current scanning and output power are similar to the DBR section222current scanning's results. When the gain section226of the laser220is biased at its threshold above (e.g., two times the threshold current), the laser220output power also appears to undulate when the gain section226and the DBR section222bias currents are kept constant. The DBR optimal bias current values may be found inFIG. 5by averaging two adjacent power peak502,504current values. For the results shown inFIG. 6, the laser220gain section226was biased at two times the threshold current, and the DBR section222was biased at about 11.8 mA.

FIGS. 7-13show experimental results for various parameters of the tunable ONU Tx200.FIG. 7is a graph that shows the curve of DBR section222laser220output power versus DBR section222injection current for the self-characterization tunable ONU Tx200shown inFIG. 2.FIG. 8is a graph that shows the curve of the laser220wavelength as a function of the DBR section222injection current for the self-characterization tunable ONU Tx200shown inFIG. 2.FIG. 9is a graph that shows the laser220output power as a function of the DBR section222injection current for the self-characterization tunable ONU Tx200shown inFIG. 2.FIG. 10is a graph that shows the DBR laser side mode suppression ratio (SMSR) as a function of the DBR section222injection current for the self-characterization tunable ONU Tx200shown inFIG. 2.FIG. 11is a graph that shows the laser220output power as a function of the phase section224injection current for the self-characterization tunable ONU Tx200shown inFIG. 2.FIG. 12is a graph that shows the laser220wavelength as a function of the phase section224injection current for the self-characterization tunable ONU Tx200shown inFIG. 2.FIG. 13is a table that shows tunable TOSA self-characterization results for four channels for the self-characterization tunable ONU Tx200shown inFIG. 2.

The ONU Tx200may save the laser220output power and the scanning current data of the DBR section222and the phase section224into the memory and processor unit204of the ONU Tx200. An analog to digital converter (ADC) (not shown) may be used for data saving and processing. The ONU Tx200memory and processor unit204may find the maximum and minimum output power current values and save these values into a memory in the memory and processor unit204.

FIG. 14is a flowchart illustrating an exemplary DBR section222current scanning procedure1400in accordance with a disclosed embodiment. At step1402, the gain section226of the tunable laser220is biased at two times the threshold current (or normal burst mode bias current for ONU transmitter). At step1404, the phase section224is biased at zero. At step1406, a scanning current may be applied to the DBR section222of the laser220. The PD228at the DBR mirror side may then measure the laser220output power curve at step1408. At step1410, the output power and scanning current data may be saved to the memory204of the ONU Tx200by means of an Analog to Digital Converter (ADC). At step1412, the memory and processing unit204may find the power maximum and minimum point current values and save them in memory and processing unit204for the tunable laser220DBR current set-up, after which the method1400may end.

The phase section224current scanning procedure is similar to that of the DBR section222.FIG. 15is a flowchart of an exemplary phase section224current scanning procedure1500in accordance with a disclosed embodiment. At step1502, the gain section226may be biased at two times threshold current (or normal burst mode bias current for ONU transmitter). At step1504, the DBR mirror or DBR section222may be biased at the average value of two DBR currents, which correspond to two adjacent maximum output power point currents502,504. At step1506, a scanning current may then be applied to the phase section224of the laser220, and the PD228at the DBR mirror side may measure the laser220output power data. At step1508, the output power and phase scanning current data may then be saved to the memory of memory and processing unit204of the ONU Tx200by means of an ADC. At step1510, the ONU's200memory and processing unit204may find the current value of output power maximum and minimum points and save the maximum and minimum points on the ONU Tx200memory in the memory and processing unit204for the tunable laser220phase current set-up, after which the method1500may end.

In another embodiment, the tunable laser PD power monitor may also be used as the tunable laser self-characterization power detector. There are two modes: one mode is for the laser output power control detector and another mode is for the tunable laser self-characterization power detector.FIG. 16is a schematic diagram of another self-characterization tunable ONU Tx1600in accordance with a disclosed embodiment. ONU Tx1600may comprise a DBR and phase scanning and bias current generator1602, a gain bias and RF generator1616, a submount1618comprising a tunable laser1620, a splitter1614, a PD power monitor1606, a memory and processing unit1604, an isolator1610, an optical waveguide (or fiber)1608, and a heat sink1612(with or without TEC temperature controller). Submount1618, splitter1614, isolator1610, PD power monitor1606, and optical fiber1608may be mounted on heat sink1612. Tunable laser1620may comprise a DBR section1622, a phase section1624, and a gain section1626. Otherwise, the DBR and phase scanning and bias current generator1602, the gain bias and RF generator1616, the submount1618, the tunable laser1620, the splitter1614, the PD power monitor1606, the memory and processing unit1604, the isolator1610, the optical fiber1608, and the heat sink1612may be substantially the same as the corresponding components ofFIG. 2. ONU Tx1600may differ from ONU Tx200inFIG. 2in that (1) the memory and processor unit1604may be coupled to the PD power monitor1606and (2) the PD power monitor1606is not only used as the laser1620output power control, but also used as the laser1620self-characterization PD.

The laser output power undulation from gain section1626facet output is different from the DBR section1622facet with DBR section1622and phase section1624bias current change.FIGS. 17 and 18show the laser1620output power undulation from gain section1626side facet with increasing DBR section1622and phase section1624injection current. InFIG. 17, the laser1620output power undulation from gain section1626side facet with increasing DBR section1622mirror bias current. For the results shown inFIG. 17, the gain section1626bias of the laser1620was at two times threshold current, and the phase section1624bias was about zero mA. InFIG. 18, the laser1620output power change from the gain section1626side facet with different laser1620phase section1624bias current is shown. For the results shown inFIG. 18, the gain section1626bias current was above two times the laser1620threshold current, and the DBR section1622mirror bias was about 11.8 mA (10thmode maximum output power point DBR current).

Returning toFIG. 16, for the tunable laser1620which uses one PD1606, this PD detector1606may have two functions: laser1620power monitor and the laser1620self-characterization detector. Under the condition of the tunable laser1620self-characterization mode, the PD1606may be similar to the laser1620DBR section1622mirror side detector. The output power and DBR section1622scanning current data may be saved in the memory of memory and processor unit1604of the ONU Tx1600by means of, for example, an ADC (not shown). The memory and processor unit1604may find the DBR section1622mirror bias current value, which may be related to the maximum and minimum power points. The DBR section1622mirror bias current value may be saved in a memory of the memory and processing unit1604for the use of the ONU Tx1600wavelength set up. The laser1620output power data from the gain section1622side facet output and the data of the phase section1624current may also be saved in a memory of the memory and processor unit1604by means of, for example, an ADC (not shown). The memory and processor unit1604may find the phase current values which are related to the output power maximum and minimum points and save these phase current values in a memory of the memory and processing unit1604for tunable ONU Tx1600wavelength setting. When the tunable laser1620phase section1624is tuned by changing injection current, the DBR section1622may be biased at some current value which may be related to the maximum output power point (e.g., point1702) DBR section1622current inFIG. 17. In an embodiment, the ONU Tx1600may characterize itself by means of output power undulation with DBR and phase injection current change when the tunable laser gain section is biased above its threshold current. The ONU Tx1600may analyze the output power and scanning current data and find the laser mode hopping points for a specific DBR section1920and phase section1922scanning current and save these point current values to its memory in the memory and processing unit1604. The ONU Tx1600may also find an optimal DBR section1920and phase section1922bias current by means of analyzing the scanning output power and scanning current data. These data and values may be used for ONU TX1900wavelength set-up.

FIG. 19is a schematic diagram of another type of self-characterization tunable ONU Tx1900in accordance with a disclosed embodiment. ONU Tx1900may comprise a memory and processing unit1904, a submount1916comprising a PD1912and a tunable laser1918, a DBR and phase scanning and bias current generator1902, a gain bias and RF generator1908, a heat sink1910(with or without TEC temperature controller), and an optical waveguide (or fiber)1906. The memory and processing unit1904, the submount1916, the PD1912, the tunable laser1918, the DBR and phase scanning and bias current generator1902, the gain bias and RF generator1908, the heat sink1910, and the optical fiber1906may be substantially the same as the corresponding components shown inFIG. 2. Compared with the ONU Tx200inFIG. 2, the splitter226, laser220PD power monitor220, and the optical isolator208are removed in ONU Tx1900. In addition, the DBR section1920side PD monitor1912may have two functions: tunable ONU Tx1900self-characterization and the laser1918output power monitoring.

For this type of tunable ONU Tx1900, the tunable TOSA characterization of ONU Tx1900may be the same as with ONU Tx200inFIG. 2, and the laser1918DBR and phase current set-up procedures may be the same as ONU Tx200as well. One difference between ONU Tx1900and ONU Tx200is that PD1912also monitors the laser1918output power. Since the DBR section1920and the phase section1922absorption coefficient is proportional to carrier density in the waveguide layer, the DBR section1920and the phase section1922loss may increase when their bias current increases. This will result in the DBR section1920side output power decreasing when the DBR section1920and phase section1922bias current increases even though the gain section1924facet output power may be unchanged. For this PD power monitor1912, another issue may be that the DBR section1920and the phase section1922may emit light spontaneously. This may be somewhat compensated for with free-carrier absorption loss. Fortunately, the DBR section1920side output power of the laser1918change is slow with increasing injecting current and can be corrected by adding absorption loss into the DBR section1920output power and compensating free-carrier absorption loss.

FIG. 20illustrates an embodiment of a network unit2000, which may be any device that transports and processes data through the network. For instance, the network unit2000may correspond to or may be located at an ONU, such as ONUs120described above. The network unit2000may comprise one or more ingress ports or units2010coupled to a receiver (Rx)2012for receiving signals and frames/data from other network components. The network unit2000may comprise a processor or logic unit2020to determine which network components to send data to. For example, the logic unit2020may comprise tunable ONU Tx200, memory and processor unit204, and/or gain bias and RF generator206. The logic unit2020may be implemented using hardware, software, or both. The network unit2000may also comprise one or more egress ports or units2030coupled to a transmitter (Tx)2032for transmitting signals and frames/data to the other network components. As such, the logic unit2020and transmitter2032may implement or support the Self-Characterization Tunable ONU procedures described above. The components of the network unit2000may be arranged as shown inFIG. 20.

The disclosed TOSA may have many advantages over the prior art. For example, current commercially available tunable transceivers are characterized manually. However, the disclosed self-characterizing tunable optical transceiver may characterize itself automatically. When the environment (e.g., temperature, etc.) of the tunable optical transceiver changes, the wavelength of the emitted radiation from the transmitter may drift, but the disclosed self-characterizing tunable optical transmitter may re-characterize itself automatically to readjust the wavelength. Additionally, in contrast to current commercially available tunable transmitters that require a wavelength locker to maintain the wavelength at a constant value and a thermoelectric cooler (TEC) to maintain a constant temperature, the disclosed tunable transmitter may not require a wavelength locker in order to maintain a constant wavelength, nor does the disclosed tunable transmitter require a TEC to maintain a constant temperature. Thus, the cost to fabricate and maintain an ONU utilizing the disclosed self-characterizing tunable optical transmitter may be lower than currently commercially available ONUs.